Gollem before 3.0.13, as used in Horde Groupware Webmail Edition 5.2.22 and other products, is affected by a reflected Cross-Site Scripting (XSS) vulnerability via the HTTP GET dir parameter in the browser functionality, affecting breadcrumb output. An attacker can obtain access to a victim's webmail account by making them visit a malicious URL.
https://lists.horde.org/archives/gollem/Week-of-Mon-20200420/001990.html
https://lists.horde.org/archives/announce/2020/001289.html
https://lists.debian.org/debian-lts-announce/2020/05/msg00033.html
https://github.com/horde/gollem/commits/master
https://github.com/horde/gollem/blob/95b2a4212d734f1b27aaa7a221d2fa1370d2631f/docs/CHANGES