CVE-2026-2578 Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts

Mattermost versions 11.3.x = 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event.. Mattermost Advisory ID: MMSA-2026-00579...

CVE-2026-2578

Mattermost (version 11.3.x, affected range up to 11.3.0) has a vulnerability where the redacted state of burn-on-read posts is not preserved during deletion. This allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event. CVSS v3.1 base score ...