CVE-2017-18920: Mattermost Server

Critical severity, CVSS 9.8. EPSS: 1.2% chance of exploitation in the next 30 days.

An issue was discovered in Mattermost Server before 3.6.2. The WebSocket feature does not follow the Same Origin Policy.

Affected products

• Mattermost Mattermost Server: before 3.6.2 (fixed in 3.6.2)

Published 2020-06-19. Last modified 2026-06-17.