CVE-2025-66488

Summary

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.

Affected Software

VendorProductVersion RangeStatus
discoursediscourse< 3.5.4affected
discoursediscourse>= 2025.11.0-latest, < 2025.11.2affected
discoursediscourse>= 2025.12.0-latest, < 2025.12.1affected
discoursediscourse>= 2026.1.0-latest, < 2026.1.0affected

Weaknesses

  • CWE-116: CWE-116: Improper Encoding or Escaping of Output

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References