Matan Berson

A Code Injection vulnerability was identified in GitHub Enterprise Server that allowed attackers to inject malicious code into the query selector via the `identity` property in the message handling function. This enabled the exfiltration of sensitive data by manipulating the DOM, including authentication tokens. To execute the attack, the victim must be logged into GitHub and interact with the attacker-controlled malicious webpage containing the hidden iframe. This vulnerability occurs due to an improper sequence of validation, where the origin check occurs after accepting the user-controlled `identity` property.

The issue is related to Reflected Cross-Site Scripting via the `msg` parameter due to insufficient input sanitization and output escaping. This allows unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.