GHSA-fmqf-pmcm-8cx9 Mattermost doesn't validate user channel membership when attaching Mattermost posts as comments to Jira issues

• Go github.com/mattermost/mattermost/server/v8: < 8.0.0-20251121122154-b57c297c6d7 → fixed in 8.0.0-20251121122154-b57c297c6d7 • Go github.com/mattermost/mattermost-server: >= 10.11.0, < 10.11.8 → fixed in 10.11.8 • Go github.com/mattermost/mattermost-server: >= 10.12.0, < 10.12.4 → fixed in 10.12.4 • Go github.com/mattermost/mattermost-server: >= 11.0.0, < 11.0.6 → fixed in 11.0.6 • Go github.com/mattermost/mattermost-server: >= 11.1.0, < 11.1.1 → fixed in 11.1.1

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.