An issue was discovered in views/list.py
in GNU Mailman Postorius before 1.3.5. An attacker (logged into any account) can send a crafted POST request to unsubscribe any user from a mailing list, also revealing whether that address was subscribed in the first place.
bugs.debian.org/cgi-bin/bugreport.cgi?bug=993746
gitlab.com/mailman/postorius
gitlab.com/mailman/postorius/-/commit/3d880c56b58bc26b32eac0799407d74b64b7474b
gitlab.com/mailman/postorius/-/issues/531
gitlab.com/mailman/postorius/-/tags
nvd.nist.gov/vuln/detail/CVE-2021-40347
phabricator.wikimedia.org/T289798
www.debian.org/security/2021/dsa-4970