Cross-site scripting vulnerability in Mailman 2.1.26 and earlier allows remote authenticated attackers to inject arbitrary web script or HTML via unspecified vectors.
https://www.debian.org/security/2018/dsa-4246
https://usn.ubuntu.com/4348-1/
https://security.gentoo.org/glsa/201904-10
https://mail.python.org/pipermail/mailman-announce/2018-June/000236.html
https://lists.debian.org/debian-lts-announce/2018/07/msg00034.html