Hi,

The following vulnerability was published for shaarli.

CVE-2026-48821[0]:
| Shaarli is a personal bookmarking service. Versions 0.16.1 and prior
| contain a DOM-based Cross-Site Scripting (XSS) vulnerability in the
| Thumbnail Synchronizer feature. When an administrator runs the
| thumbnail update process, malicious bookmark titles are returned via
| an AJAX response and inserted into the DOM using innerHTML without
| proper sanitization. The issue originates from the interaction
| between the backend thumbnail update endpoint and the frontend
| JavaScript responsible for rendering update progress. On the
| backend, the ThumbnailsController::ajaxUpdate method returns
| bookmark data formatted using the 'raw' formatter. This includes the
| unescaped bookmark title in the JSON response. On the client side,
| the script thumbnails-update.js processes this AJAX response and
| dynamically updates the progress interface. Administrators using the
| thumbnail synchronization feature are affected and exploitation
| could lead to session hijacking, privilege escalation, backdoor
| injection and full compromise. This issue has been fixed in version
| 0.16.2.


If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-48821
https://www.cve.org/CVERecord?id=CVE-2026-48821
[1] https://github.com/shaarli/Shaarli/security/advisories/GHSA-mw63-f9qj-c5h3

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore