CVE-2026-55674
Published:August 17, 2026
Updated:September 01, 2026
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.
Affected Packages
https://github.com/discourse/discourse.git (GITHUB):
Affected version(s) >=v2026.5.0 <v2026.5.2Fix Suggestion:
Update to version v2026.5.2https://github.com/discourse/discourse.git (GITHUB):
Affected version(s) =v2026.6.0 <v2026.6.1Fix Suggestion:
Update to version v2026.6.1https://github.com/discourse/discourse.git (GITHUB):
Affected version(s) >=v2026.1.0 <v2026.1.6Fix Suggestion:
Update to version v2026.1.6Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
9.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
HIGH
Subsequent System Integrity
HIGH
Subsequent System Availability
NONE
CVSS v3
Base Score:
9.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
EPSS
Base Score:
0.36