CVE-2026-43887: Outline

High severity, CVSS 7.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Outline Outline: from 0.84.0, before 1.7.0 (fixed in 1.7.0)

Published 2026-05-11. Last modified 2026-06-17.