GitLab CE/EE Cross-Site Scripting Vulnerability in Markdown Placeholder Processing

A cross-site scripting vulnerability has been identified in GitLab Community Edition (CE) and Enterprise Edition (EE) versions 10.6 prior to 18.7.6, 18.8 prior to 18.8.6, and 18.9 prior to 18.9.2. This vulnerability could have allowed an authenticated user to inject JavaScript into a browser when the 'markdown_placeholders' feature flag was enabled. The issue arises from improper sanitization of placeholder content during markdown processing, which could have been exploited to execute malicious scripts in the context of the user's browser.

Impact

Exploitation of this vulnerability could lead to cross-site scripting, allowing for the injection and execution of malicious JavaScript in the user's browser.

Remediation

Users are advised to upgrade to GitLab versions 18.9.2, 18.8.6, or 18.7.6. Instructions for updating GitLab can be found on the GitLab Update page. For GitLab Runner, refer to the Updating the Runner page.