Shaarli up to 0.16.1 Thumbnail Synchronizer Feature thumbnails-update.js ajaxUpdate cross site scripting

Summaryinfo

A vulnerability was found in Shaarli up to 0.16.1. It has been classified as problematic. This impacts the function ThumbnailsController::ajaxUpdate of the file thumbnails-update.js of the component Thumbnail Synchronizer Feature. This manipulation causes cross site scripting. The identification of this vulnerability is CVE-2026-48821. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Shaarli up to 0.16.1. It has been declared as problematic. Affected by this vulnerability is the function ThumbnailsController::ajaxUpdate of the file thumbnails-update.js of the component Thumbnail Synchronizer Feature. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-48821 since 05/22/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 0.16.2 eliminates this vulnerability. The upgrade is hosted for download at github.com.

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Productinfo

Name

• Shaarli

Version

• 0.16.0
• 0.16.1

Website

• Product: https://github.com/shaarli/Shaarli/

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