XSS in Shaarli
CVE-2026-48821
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.002 (7.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.001
Affected products
- Shaarli — versions < 0.16.2
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-48821?
- CVE-2026-48821 is a medium-severity vulnerability in Shaarli, classified under Cross-site Scripting. CVSS score: 5.8/10. Published 2026-06-17.
- How severe is CVE-2026-48821?
- Medium severity. CVSS v3 base score is 5.8 out of 10.