All vulnerabilities
CVE-2026-91119GHSA-pv3p-p3m9-v8v3

Discourse: Encode action_code_who in mention URLs

discourse discourseApplications & CMS
Open in ThreatlineRecord JSON
CVSS
6.4Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.20%Chance of exploitation activity in the next 30 days, higher than 9% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in2026.8.0Also 2026.7.2, 2026.6.3 and 1 moreGitHub
Published24 Sep 2026Updated 28 Sep 2026CVE List

What fixes it

  • 2026.8.0Discourse, otherGitHub
  • 2026.7.2Discourse, otherGitHub
  • 2026.6.3Discourse, otherGitHub
  • 2026.1.8Discourse, otherGitHub

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from CVE List

Affected versions 8

  • discourseaffected: < 2026.8.0CVE List
  • discourseaffected: >= 2026.7.0-latest, < 2026.7.2CVE List
  • discourseaffected: >= 2026.6.0-latest, < 2026.6.3CVE List
  • discourseaffected: >= 2026.1.0-latest, < 2026.1.8CVE List
  • Discourse, other>= 0GitHub
  • Discourse, other>= 2026.7.0-latestGitHub
  • Discourse, other>= 2026.6.0-latestGitHub
  • Discourse, other>= 2026.1.0-latestGitHub

References 6