CVE-2019-20847: Mattermost Server

Medium severity, CVSS 5.3. EPSS: 0.8% chance of exploitation in the next 30 days.

An issue was discovered in Mattermost Server before 5.18.0. An attacker can send a user_typing WebSocket event to any channel.

Affected products

• Mattermost Mattermost Server: before 5.18.0 (fixed in 5.18.0)

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