CVE-2026-8821

Mattermost versions 11.9.0, 11.8.4, 11.7.7, and 10.11.22 (and below within their respective branches) contain a permission bypass in the Playbooks feature. During playbook run creation, the system fails to validate the channel member-management permission, allowing an authenticated channel member...

EUVD-2026-77371

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate channel member-management permission during playbook run creation, allowing an authenticated channel member to add an arbitrary user to a restricted channel via the run owner field...