XSS in Discourse
CVE-2026-91119
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topic small-action and nested-activity-log components interpolated the free-form action_code_who value into mention-link href attributes without URL encoding. A quote-bearing display name could terminate the intended URL attribute and inject attacker-controlled elements into the trusted rendered markup. Although the visible mention text was escaped, the unencoded path component allowed stored HTML injection when another user viewed the affected topic action or activity log. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Discourse — versions < 2026.8.0, >= 2026.1.0-latest, < 2026.1.8, >= 2026.6.0-latest, < 2026.6.3
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-pv3p-p3m9-v8v3
- github.com/discourse/discourse/pull/42882
- github.com/discourse/discourse/commit/20dbf112760eb1d6a58f2e49aeef7546898b6f1c
- github.com/discourse/discourse/commit/66653c484cfb91bc346f9a326f6945387f17b035
- github.com/discourse/discourse/commit/77a81c7a3a7ff9e94b355e32b8f379f2d389e05a
- github.com/discourse/discourse/commit/c4748f651d9d2f3a6dd3106a4d5564536c645168
Frequently asked questions
- What is CVE-2026-91119?
- CVE-2026-91119 is a medium-severity vulnerability in Discourse, classified under Cross-site Scripting. CVSS score: 6.4/10. Published 2026-09-24.
- How severe is CVE-2026-91119?
- Medium severity. CVSS v3 base score is 6.4 out of 10.