Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

GHSA-XVCX-MGPC-5XH3 Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6339

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6339 Missing request origin validation on burn-on-read reveal endpoint

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6339

Mattermost contains a vulnerability (CVE-2026-6339) in versions 11.5.x <= 11.5.1 and 11.4.x

PT-2026-41657

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.4.x through 11.4.3 Mattermost versions 11.5.x through 11.5.1 Description An issue exists where the burn-on-read reveal endpoint fails to validate the 'X-Requested-With' header. This allows an authenticated channel member...