HumHub Community Edition 1.19.0 contains a stored cross-site scripting vulnerability in the friendship confirmation dialog. An authenticated low-privileged member can save HTML in their first and last name. When another authenticated user clicks Friends for that profile, HumHub places the decoded display name into a modal through jQuery html(), causing attacker-controlled markup to execute in the victim's HumHub origin.
If an immediate upgrade is not possible, disable the friendship feature or restrict profile editing to trusted users. Review existing profile names for markup, but treat cleanup as a temporary mitigation rather than a fix.
Upgrade the current line to HumHub 1.19.2 or later (1.19.3 is the current release), or the 1.18 maintenance line to 1.18.7 or later. The vendor fixed the issue in 1.19.1 and 1.18.7; 1.19.1 was not separately released.