CVE-2019-20887: Mattermost Server

Medium severity, CVSS 4.3. EPSS: 0.7% chance of exploitation in the next 30 days.

An issue was discovered in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6. It does not honor flags API permissions when deciding whether a user can receive intra-team posts.

Affected products

• Mattermost Mattermost Server: before 4.10.6 (fixed in 4.10.6); from 5.5.0, before 5.5.3 (fixed in 5.5.3); from 5.6.0, before 5.6.4 (fixed in 5.6.4); from 5.7.0, before 5.7.1 (fixed in 5.7.1)

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