CVE-2026-53963: Discourse

Critical severity, CVSS 9.0. EPSS: 0.7% chance of exploitation in the next 30 days.

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, a malicious second factor name on an attacker-controlled account was not escaped in the delete confirmation dialog, allowing stored cross-site scripting when an administrator impersonated that account. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

Affected products

• Discourse Discourse: from 2026.1.0, before 2026.1.5 (fixed in 2026.1.5); from 2026.4.0, before 2026.4.2 (fixed in 2026.4.2); from 2026.5.0, before 2026.5.1 (fixed in 2026.5.1); version 2026.6.0 only

Published 2026-07-09. Last modified 2026-07-14.