GNU Mailman 2.x before 2.1.30 uses the .obj extension for scrubbed application/octet-stream MIME parts. This behavior may contribute to XSS attacks against list-archive visitors, because an HTTP reply from an archive web server may lack a MIME type, and a web browser may perform MIME sniffing, conclude that the MIME type should have been text/html, and execute JavaScript code.
bazaar.launchpad.net/~mailman-coders/mailman/2.1/view/head:/NEWS
lists.opensuse.org/opensuse-security-announce/2020-10/msg00047.html
lists.opensuse.org/opensuse-security-announce/2020-10/msg00063.html
www.openwall.com/lists/oss-security/2020/04/24/3
lists.debian.org/debian-lts-announce/2020/05/msg00002.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6YCMGTTOXXCVM4O6CYZLTZDX6YLYORNF/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G4COSBBEMJYLV7WSW5QTUJUOFJFK47KK/
usn.ubuntu.com/4348-1/
www.debian.org/security/2020/dsa-4664
www.openwall.com/lists/oss-security/2020/02/24/2
www.openwall.com/lists/oss-security/2020/02/24/3