CVE-2026-72720: Discourse

Medium severity, CVSS 6.4. EPSS: 0.4% chance of exploitation in the next 30 days.

Discourse is an open-source discussion platform. Prior to 2026.1.7, 2026.6.2, 2026.7.1, and 2026.8.0-latest.1, Discourse has HTML injection in PrettyText.format_for_email because cooked attribute values are reparsed as markup. Crafted Vimeo iframe sources, secure-upload URLs or dimensions, and hashtag data-slug values can cause decoded attribute text to be reinterpreted as HTML. The vulnerable conversion also fails to strictly validate the Vimeo iframe host and path, allowing non-Vimeo allowlisted iframes to be converted. This issue is fixed in versions 2026.1.7, 2026.6.2, 2026.7.1, and 2026.8.0-latest.1.

Affected products

• Discourse Discourse: before 2026.1.7 (fixed in 2026.1.7); from 2026.6.0-latest, before 2026.6.2 (fixed in 2026.6.2); from 2026.7.0-latest, before 2026.7.1 (fixed in 2026.7.1); from 2026.8.0-latest, before 2026.8.0-latest.1 (fixed in 2026.8.0-latest.1)

Published 2026-08-10. Last modified 2026-09-08.