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Vulnerability record · CVE-2026-91122 · published 24 September 2026

CVE-2026-91122: Cross-site scripting vulnerability

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

8.7 CVSS 3.1 High EPSS 0.26% · top 84.0% CWE-79 · Cross-site scripting Deferred
8.7CVSS 3.1 base score
0.26%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
6References
24 Sep 2026Last modified by NVD

Description

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

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

References

LinkTags
https://github.com/discourse/discourse/commit/05d92b8749f68d2626cbe65ec7adde7562a0283d
https://github.com/discourse/discourse/commit/5674b3e6594825c28d2678e55057fd6802f11031
https://github.com/discourse/discourse/commit/c3993e318e172389be5c98455177876f1dd87dda
https://github.com/discourse/discourse/commit/d7126af3264b672d2201d84c18a37cb8627424a8
https://github.com/discourse/discourse/pull/42882
https://github.com/discourse/discourse/security/advisories/GHSA-8m44-f6g9-7cg7

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Source: NIST National Vulnerability Database (record CVE-2026-91122), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.