Stored XSS in Shaarli Bookmarking Service

Impact Analysis

This vulnerability can impact users by allowing attackers to execute arbitrary JavaScript code in the context of the affected application. This can lead to theft of sensitive information such as session cookies, unauthorized actions performed on behalf of users, or other malicious activities. Both administrators and privileged users who interact with the "Filter by tag" feature are at risk. The impact includes potential compromise of confidentiality and integrity of user data.

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Mitigation Strategies

To mitigate this vulnerability, upgrade Shaarli to version 0.16.2 or later, where the stored Cross-Site Scripting (XSS) issue in the tag filtering functionality has been fixed.

Avoid using the "Filter by tag" search feature with untrusted or suspicious tags until the upgrade is applied.

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Compliance Impact

The vulnerability is a stored Cross-Site Scripting (XSS) issue in Shaarli versions 0.16.1 and prior, allowing authenticated users to inject arbitrary JavaScript into the tags field. This can lead to unauthorized script execution when users interact with the tag filtering functionality.

Such XSS vulnerabilities can impact compliance with standards like GDPR and HIPAA because they may lead to unauthorized access or exposure of sensitive user data, compromise user privacy, and violate requirements for protecting personal information.

Specifically, GDPR mandates appropriate technical measures to ensure data security and prevent unauthorized processing, while HIPAA requires safeguards to protect electronic protected health information (ePHI). An XSS vulnerability could be exploited to bypass these safeguards.

Therefore, this vulnerability could negatively affect compliance with these regulations until it is remediated, as it exposes the application to potential data breaches or unauthorized actions.

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Executive Summary

This vulnerability is a stored Cross-Site Scripting (XSS) issue found in Shaarli versions 0.16.1 and earlier. It occurs in the tag filtering functionality where an authenticated user can inject arbitrary JavaScript code into the tags field when creating a bookmark. The malicious script is stored in the database and later executed when users interact with the "Filter by tag" search feature on the homepage. This happens because user input in the tags field is not properly sanitized or escaped before being displayed, allowing the injected script to run in the context of other users.

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Detection Guidance

This vulnerability involves stored Cross-Site Scripting (XSS) in the tag filtering functionality of Shaarli versions 0.16.1 and prior. Detection involves checking for malicious JavaScript payloads stored in the tags field of bookmarks.

To detect this vulnerability on your system, you can:

• Review the tags stored in the Shaarli database for suspicious or unexpected JavaScript code or HTML event handlers.
• Use database query commands to extract tags and inspect them for script tags or event handler attributes (e.g., onclick, onmouseover). For example, if using SQLite, you might run a query like: SELECT tags FROM bookmarks WHERE tags LIKE '%<script%' OR tags LIKE '%on%=%';
• Manually test the "Filter by tag" feature in the Shaarli web interface by inputting tags containing JavaScript payloads to see if they execute.

Note that this vulnerability requires authenticated access to create malicious tags, so detection commands should be run with appropriate permissions.

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