Mark Sapiro reports:
A content injection vulnerability via the options login page has
been discovered and reported by Vishal Singh.
An issue similar to CVE-2018-13796 exists at different endpoint & param. It can lead to a phishing attack.
(added 2020-05-07) This is essentially the same as
https://bugs.launchpad.net/mailman/+bug/1873722 except the vector is
the private archive login page and the attack only succeeds if the
list's roster visibility (private_roster) setting is 'Anyone'.