Roundcube before 1.3.17 and 1.4.x before 1.4.12 is prone to XSS in handling an attachment's filename extension when displaying a MIME type warning message.
https://www.debian.org/security/2021/dsa-5013
https://lists.debian.org/debian-lts-announce/2021/12/msg00004.html
https://github.com/roundcube/roundcubemail/issues/8193
https://github.com/roundcube/roundcubemail/commit/faf99bf8a2b7b7562206fa047e8de652861e624a
https://github.com/roundcube/roundcubemail/commit/7d7b1dfeff795390b69905ceb63d6391b5b0dfe7