CVE-2025-66488

Discourse allows script execution in uploaded HTML/XML files on S3

State: Published
Severity: 4.6 Medium
Published: Jan 28, 2026
Updated: Jan 28, 2026
Reserved: Dec 2, 2025

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	4.6 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L	GitHub_M

Weaknesses

CWE-116 Improper Encoding or Escaping of Output

Affected Products

Product	Versions
discoursediscourse	< 3.5.4Affected >= 2025.11.0-latest, < 2025.11.2Affected >= 2025.12.0-latest, < 2025.12.1Affected >= 2026.1.0-latest, < 2026.1.0Affected

References

https://github.com/discourse/discourse/security/advisories/GHSA-68jp-3934-62rx

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