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Discourse CVE-2026-33395

MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-03-19 GitHub_M
XSS Discourse
4.4
CVSS 3.1 · GitHub Advisory
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Severity by source

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

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

CVSS VectorGitHub Advisory

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

Lifecycle Timeline

2
Analysis Generated
Mar 19, 2026 - 23:00 vuln.today
CVE Published
Mar 19, 2026 - 22:33 nvd
MEDIUM 4.4

DescriptionGitHub Advisory

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the discourse-graphviz plugin contains a stored cross-site scripting (XSS) vulnerability that allows authenticated users to inject malicious JavaScript code through DOT graph definitions. For instances with CSP disabled only. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, disable the graphviz plugin, upgrade to a patched version, or enable a content security policy.

AnalysisAI

Authenticated users can inject persistent JavaScript through malicious DOT graph definitions in the discourse-graphviz plugin on Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, enabling stored XSS attacks when Content Security Policy is disabled. Affected instances should upgrade to patched versions, disable the plugin, or enforce a CSP as a temporary mitigation, as no patch is currently available for all deployment scenarios.

Technical ContextAI

Cross-site scripting (XSS) allows injection of client-side scripts into web pages viewed by other users due to insufficient output encoding.

RemediationAI

Encode all user-supplied output contextually (HTML, JS, URL). Implement Content Security Policy (CSP) headers. Use HTTPOnly and Secure cookie flags.

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CVE-2026-33395 vulnerability details – vuln.today
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