GHSA-rp4v-qc77-phm4 Mattermost doesn't restrict role_updated websocket event broadcasts to members of the affected team or channel

• Go github.com/mattermost/mattermost-server: >= 11.6.0, < 11.6.1 → fixed in 11.6.1 • Go github.com/mattermost/mattermost-server: >= 11.5.0, < 11.5.5 → fixed in 11.5.5 • Go github.com/mattermost/mattermost-server: >= 10.11.0, < 10.11.17 → fixed in 10.11.17 • Go github.com/mattermost/mattermost/server/v8: >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260504071740-9408b98025d7 → fixed in 8.0.0-20260504071740-9408b98025d7

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to restrict role_updated websocket event broadcasts to members of the affected team or channel, which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection. Mattermost Advisory ID: MMSA-2026-00616