GHSA-q453-638c-h4mr Mattermost Fails to Validate Remote Cluster Upload Sessions

• Go github.com/mattermost/mattermost-server: >= 10.8.0, < 10.8.4 → fixed in 10.8.4 • Go github.com/mattermost/mattermost-server: >= 10.5.0, < 10.5.9 → fixed in 10.5.9 • Go github.com/mattermost/mattermost-server: >= 9.11.0, < 9.11.18 → fixed in 9.11.18 • Go github.com/mattermost/mattermost-server: >= 10.9.0, < 10.9.3 → fixed in 10.9.3 • Go github.com/mattermost/mattermost-server: >= 10.10.0, < 10.10.1 → fixed in 10.10.1 • Go github.com/mattermost/mattermost/server/v8: < 8.0.0-20250708173752-d6b35c41f0ae5 → fixed in 8.0.0-20250708173752-d6b35c41f0ae5 • Go github.com/mattermost/mattermost-server/v5: <= 5.39.3 (no fix yet) • Go github.com/mattermost/mattermost-server/v6: <= 5.7.2 (no fix yet)

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2, 10.10.x <= 10.10.0 fail to validate upload types in remote cluster upload sessions which allows a system admin to upload non-attachment file types via shared channels that could potentially be placed in arbitrary filesystem directories.