I get the occasional email from roundup with:

Traceback (most recent call last):
  File "/home/app-roundup/roundup/lib/roundup/cgi/client.py", line 836, in inner_main
    csrf_ok = self.handle_csrf()
              ^^^^^^^^^^^^^^^^^^
  File "/home/app-roundup/roundup/lib/roundup/cgi/client.py", line 1646, in handle_csrf
    if '@csrf' in self.form:
       ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/cgi.py", line 584, in __contains__
    raise TypeError("not indexable")
TypeError: not indexable


Presumably, someone is posting rubbish to the URL; it can be reproduced using:

curl -X POST https://issues.example.com/ -H "Content-Type: text/plain" -d "test"

(replacing issues.example.com with a roundup instance)