FreshRSS up to 1.26.1 SVG Favicon f.php fetch cross site scripting

Summaryinfo

A vulnerability was found in FreshRSS up to 1.26.1. It has been declared as problematic. This affects the function fetch of the file f.php of the component SVG Favicon Handler. Such manipulation leads to cross site scripting. This vulnerability is listed as CVE-2025-31136. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in FreshRSS up to 1.26.1 and classified as problematic. Affected by this issue is the function fetch of the file f.php of the component SVG Favicon Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to 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. Impacted is integrity. CVE summarizes:

FreshRSS is a self-hosted RSS feed aggregator. Prior to version 1.26.2, it's possible to run arbitrary JavaScript on the feeds page. This occurs by combining a cross-site scripting (XSS) issue that occurs in `f.php` when SVG favicons are downloaded from an attacker-controlled feed containing `` tags inside of them that aren't sanitized, with the lack of CSP in `f.php` by embedding the malicious favicon in an iframe (that has `sandbox="allow-scripts allow-same-origin"` set as its attribute). An attacker needs to control one of the feeds that the victim is subscribed to, and also must have an account on the FreshRSS instance. Other than that, the iframe payload can be embedded as one of two options. The first payload requires user interaction (the user clicking on the malicious feed entry) with default user configuration, and the second payload fires instantly right after the user adds the feed or logs into the account while the feed entry is still visible. This is because of lazy image loading functionality, which the second payload bypasses. An attacker can gain access to the victim's account by exploiting this vulnerability. If the victim is an admin it would be possible to delete all users (cause damage) or execute arbitrary code on the server by modifying the update URL using fetch() via the XSS. Version 1.26.2 has a patch for the issue.

The advisory is available at github.com. This vulnerability is handled as CVE-2025-31136 since 03/26/2025. The exploitation is known to be difficult. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

By approaching the search of inurl:f.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.26.2 eliminates this vulnerability.

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Productinfo

Name

• FreshRSS

Version

• 1.26.0
• 1.26.1

Website

• Product: https://github.com/FreshRSS/FreshRSS/

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