Wikimedia MediaWiki FlexDiagrams Extension Stored Cross-Site Scripting Vulnerability

A stored cross-site scripting vulnerability has been identified in the FlexDiagrams extension for MediaWiki. This issue arises from improper input sanitization during web page generation, allowing malicious HTML to be injected and saved. The vulnerability affects the master version of the FlexDiagrams extension.

Impact

Exploitation of this vulnerability allows for stored cross-site scripting, where injected scripts are executed in the context of the user viewing the affected page.

Reproduction

To reproduce this vulnerability, create a Drawio diagram and save it. Then, navigate to the diagram's page using the 'edit diagram' action with the 'x-xss' language parameter. This will trigger the stored XSS by executing the injected script.

Remediation

Users can update to the patched version of the FlexDiagrams extension available on the Wikimedia Gerrit repository.