CVE-2026-55674

critical · 9.3

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, an unauthenticated attacker could send a single request with a crafted color_scheme_id (or dark_scheme_id) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered into a color scheme tag without escaping, the attacker could break out of the attribute and inject a tag that bypassed Discourse's nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors' browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

9.3

CVSS

0.6%

EPSS (exploit prob.)

46th

EPSS percentile

2026-08-17

Published

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

Weaknesses

CWE-79

References

https://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2g

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-55674