Vulnerability Description
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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/shaarli/Shaarli/releases/tag/v0.16.2
- https://github.com/shaarli/Shaarli/security/advisories/GHSA-mw63-f9qj-c5h3
- https://github.com/shaarli/Shaarli/security/advisories/GHSA-mw63-f9qj-c5h3
FAQ
What is CVE-2026-48821?
CVE-2026-48821 is a vulnerability with a CVSS score of 5.8 (MEDIUM). 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 ...
How severe is CVE-2026-48821?
CVE-2026-48821 has been rated MEDIUM with a CVSS base score of 5.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-48821?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.