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CVE-2025-66488

Good to know:

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Date: January 28, 2026

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.

Severity Score

Related Resources (3)

https://nvd.nist.gov/vuln/detail/CVE-2025-66488
https://github.com/discourse/discourse/security/advisories/GHSA-68jp-3934-62rx
https://www.mend.io/vulnerability-database/CVE-2025-66488

Severity Score

Weakness Type (CWE)

Improper Encoding or Escaping of Output

CWE-116

Top Fix

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Upgrade Version

Upgrade to version https://github.com/discourse/discourse.git - v2026.1.0;https://github.com/discourse/discourse.git - v2025.11.2;https://github.com/discourse/discourse.git - v3.5.4;https://github.com/discourse/discourse.git - v2025.12.0

Learn More

CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): LOW
Privileges Required (PR): LOW
User Interaction (UI): REQUIRED
Scope (S): UNCHANGED
Confidentiality (C): NONE
Integrity (I): LOW
Availability (A): LOW

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