Cross-site scripting (XSS) vulnerability in the web UI in Mailman before 2.1.26 allows remote attackers to inject arbitrary web script or HTML via a user-options URL.
https://www.mail-archive.com/mailman-users%40python.org/msg70375.html
https://www.debian.org/security/2018/dsa-4108
https://usn.ubuntu.com/3563-1/
https://lists.debian.org/debian-lts-announce/2018/02/msg00007.html
https://bugs.launchpad.net/mailman/+bug/1747209
https://access.redhat.com/errata/RHSA-2018:0505