Gogs up to 0.14.2 /-/api/sanitize_ipynb bluemonday.UGCPolicy cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in Gogs up to 0.14.2. The affected element is the function bluemonday.UGCPolicy of the file /-/api/sanitize_ipynb. Executing a manipulation can lead to cross site scripting. The identification of this vulnerability is CVE-2026-52816. The attack may be launched remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Gogs up to 0.14.2. This vulnerability affects the function bluemonday.UGCPolicy of the file /-/api/sanitize_ipynb. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-80. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as "<", ">", and "&" that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. As an impact it is known to affect integrity. CVE summarizes:

Gogs is an open source self-hosted Git service. Prior to 0.14.3, the Jupyter Notebook (ipynb) sanitizer endpoint at POST /-/api/sanitize_ipynb allows arbitrary data: URIs without proper restrictions, potentially leading to Cross-Site Scripting (XSS). The endpoint uses bluemonday.UGCPolicy() with p.AllowURLSchemes("data") which permits all data URI schemes including data:text/html, enabling attackers to inject malicious HTML/JavaScript. Additionally, the endpoint has no authentication middleware, allowing any registered user to exploit this vulnerability. This vulnerability is fixed in 0.14.3.

The advisory is available at github.com. This vulnerability was named CVE-2026-52816 since 06/08/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. 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.

Upgrading to version 0.14.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch dd1bd9837aa196b3ed3a8ee21e5727b5d7a986a3 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• Gogs

Version

• 0.14.0
• 0.14.1
• 0.14.2

License

• open-source

Website

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

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