SEPTEMBER 17, 2026
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Case File

CVE-2026-55674

CRITICAL · CVSS 9.3 EPSS 0.36% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-17 · Last synced 2026-09-16

CyberRota Analysis

AI-Generated

Discourse versions prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0 are vulnerable to an unauthenticated attack that allows the injection of arbitrary HTML and JavaScript via manipulated cookie values. This vulnerability can lead to cross-site scripting (XSS) attacks, compromising the security of users' browsers and potentially exposing sensitive information. Organizations using affected versions of Discourse should prioritize upgrading to the patched releases to mitigate this critical risk.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-55674
Severity
CRITICAL
CVSS
9.3
EPSS
0.36%
Java

Original NVD Description

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.