CVE-2026-43887 Outline: Stored XSS via Comment Mentions
Attackers can execute arbitrary JavaScript in victim browsers by injecting malicious href attributes into comment mentions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-43887?
CVE-2026-43887 is a high-severity cross-site scripting vulnerability in outline, published on 11 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Outline is a service that allows for collaborative documentation. From 0.84.0 to 1.6.1, the Outline comment section permits users to mention other users; however, the backend does not validate or sanitize the href attribute associated with these mentions. As a result, potentially dangerous protocols (e.g., javascript:) are not filtered, introducing a risk of client-side code execution. This vulnerability is fixed in 1.7.0.
Weakness: CWE-79
Which versions are affected by CVE-2026-43887?
How do I fix CVE-2026-43887?
No fix has been published for CVE-2026-43887 yet. Limit exposure of the affected software until one is available.
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-2026-43887 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43887 exists.
Sources
Also known as GHSA-rqrg-f3qc-xvgh.