Mattermost versions 9.6.0, 9.5.x before 9.5.3, and 8.1.x before 8.1.12 fail to fully validate role changes, which allows an attacker authenticated as a team admin to promote guests to team admins via crafted HTTP requests. https://mattermost.com/security-updates
Created purple-mattermost tracking bugs for this issue: Affects: epel-all [bug 2277340] Affects: fedora-all [bug 2277341]