CVE-2026-91119 Discourse: Encode action_code_who in mention URLs
Attackers can inject malicious HTML into Discourse activity logs via unencoded user names, potentially executing scripts in other users' browsers.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-91119?
CVE-2026-91119 is a medium-severity cross-site scripting vulnerability in discourse, published on 24 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-91119?
1 open source package ship an affected version, including discourse.
| Package | Affected | Fixed in |
|---|---|---|
discourse Bitnami | All versions | 2026.8.0 |
How do I fix CVE-2026-91119?
Upgrade discourse to 2026.8.0 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-91119 being exploited?
There is no known exploitation of CVE-2026-91119 in the wild and no public exploit code.
Sources
Also known as BIT-discourse-2026-91119, GHSA-pv3p-p3m9-v8v3.