Executive brief
Kirby CMS, a platform used for building and managing websites, contains a security flaw in its 'writer' field component. An attacker could potentially trick a site administrator into clicking a malicious link within the management panel, leading to the execution of unauthorized scripts. While primarily a 'self-XSS' issue requiring user interaction, it could lead to unauthorized actions being performed within the administrative interface.
Technical details
A self-cross-site scripting (XSS) vulnerability exists in the Kirby CMS 'writer' field and the underlying <k-writer> component. The vulnerability stems from improper neutralization of scripting links (e.g., javascript: URIs) used as targets for link or email components. While the backend typically sanitizes these values before storage, a user can trigger the execution of the script by clicking the link within the Panel interface before the content is saved. Exploitation requires social engineering to convince a Panel user to enter and then click the malicious link, or knowledge of the content structure to facilitate the attack. The issue is fixed in versions 4.9.4 and 5.4.4 by implementing more robust validation against dangerous URL schemes.
Affected products
- getkirby Kirby CMS < 4.9.4, >= 5.0.0, < 5.4.4
Timeline
- 2026-06-17: patched: Versions 4.9.4 and 5.4.4 released
- 2026-07-09: disclosed: CVE-2026-49276 published