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Discourse CVE-2025-66488

MEDIUM
Improper Encoding or Escaping of Output (CWE-116)
2026-01-28 security-advisories@github.com
XSS Discourse
4.6
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
4.6 MEDIUM
AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

Lifecycle Timeline

2
Analysis Generated
Mar 12, 2026 - 21:54 vuln.today
CVE Published
Jan 28, 2026 - 19:16 nvd
MEDIUM 4.6

DescriptionGitHub Advisory

Discourse is an open source discussion platform. A vulnerability present in versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 affects anyone who uses S3 for uploads. While scripts may be executed, they will only be run in the context of the S3/CDN domain, with no site credentials. Versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 fix the issue. As a workaround, disallow html or xml files for uploads in authorized_extensions. For existing html xml uploads, site owners can consider deleting them.

AnalysisAI

Discourse is an open source discussion platform. A vulnerability present in versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 affects anyone who uses S3 for uploads. [CVSS 4.6 MEDIUM]

Technical ContextAI

Classified as CWE-116 (Improper Encoding or Escaping of Output). Affects Discourse. Discourse is an open source discussion platform. A vulnerability present in versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 affects anyone who uses S3 for uploads. While scripts may be executed, they will only be run in the context of the S3/CDN domain, with no site credentials. Versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 fix the issue. As a workaround, disallow html or xml files for uploads in authorized_extensions. For existing html xml uploads, site owners can consider dele

RemediationAI

Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.

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CVE-2025-66488 vulnerability details – vuln.today
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