In Horde Groupware 5.2.19 and 5.2.21, there is XSS via the Color field in a Create Task List action.
https://lists.debian.org/debian-lts-announce/2020/08/msg00047.html
https://lists.debian.org/debian-lts-announce/2020/08/msg00046.html
https://github.com/horde/base/commit/fb2113bbcd04bd4a28c46aad0889fb0a3979a230