CVE-2025-66488 - CVE House
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Status published Medium CVE-2025-66488

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

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

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CVE-2025-69218
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CVE-2025-68934
Discourse Has Denial of Service (DoS) Vulnerability in Drafts Creation Endpoint
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CVE-2025-68933
Discourse non-admin moderators can exfiltrate private content via post ownership transfer
Medium 6.9
CVE-2025-68666
Discourse users archives leaked to users with moderation privileges
Medium 5.9

Affected Vendor

Affected Software

discourse
Vulnerable Versions:
< 3.5.4, >= 2025.11.0-latest, < 2025.11.2, >= 2025.12.0-latest, < 2025.12.1, >= 2026.1.0-latest, < 2026.1.0

Timeline

Official Publish: January 28th, 2026
Last Modified: January 28th, 2026
Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L

Weaknesses (CWE)

CWE-116

MITRE ATT&CK TTPs

T1189 Drive-by Compromise
Initial Access
T1190 Exploit Public-Facing Application
Initial Access
T1059 Command and Scripting Interpreter
Execution
T1565.002 Stored Data Manipulation
Impact