GHSA-rmhw-c3xr-m3xx Mattermost doesn't properly validate CSRF tokens

• Go github.com/mattermost/mattermost/server/v8: >= 11.4.0-rc1, < 11.4.1 → fixed in 11.4.1 • Go github.com/mattermost/mattermost/server/v8: >= 11.3.0-rc1, < 11.3.2 → fixed in 11.3.2 • Go github.com/mattermost/mattermost/server/v8: >= 11.2.0-rc1, < 11.2.3 → fixed in 11.2.3 • Go github.com/mattermost/mattermost/server/v8: >= 10.11.0-rc1, < 10.11.11 → fixed in 10.11.11 • Go github.com/mattermost/mattermost/server/v8: >= 8.0.0-20260105080200-d27a2195068d, < 10.11.11 → fixed in 10.11.11

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request. Mattermost Advisory ID: MMSA-2026-00578