CVE-2026-10527 Boards plugin retains Board Admin rights for users demoted to System Guest

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fails to reconcile SchemeAdmin flags with a user's current role which allows a user demoted to System Guest to retain Board Admin privileges and perform admin-only operations via the Boards REST API or UI.. Mattermost Adviso...

CVE-2026-10527

Mattermost versions up to 11.7.6, 10.11.21, and 11.8.3 fail to reconcile SchemeAdmin flags with role changes, allowing a user demoted to System Guest to retain Board Admin privileges and perform admin-only operations via the Boards REST API or UI. CVSS 6.3 MEDIUM, network exploitable with low pri...