Hanno Boeck discovered that it was possible to create a cross site scripting attack on the webarchives of the Mailman mailing list manager, by sending a special type of attachement.

For the oldstable distribution (stretch), this problem has been fixed in version 1:2.1.23-1+deb9u5.

For the stable distribution (buster), this problem has been fixed in version 1:2.1.29-1+deb10u1.

We recommend that you upgrade your mailman packages.

For the detailed security status of mailman please refer to its security tracker page at: \ https://security-tracker.debian.org/tracker/mailman