Insufficient HTML Sanitization Allows User-Controlled DOM Elements to Overwrite Server-Initialized Data Islands and Trigger Unintended Server-Side POST Requests

Vulnerability Description

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed user-supplied HTML to inject DOM elements with IDs that collided with server-initialized data islands. These collisions could overwrite or shadow critical application state objects used by certain Project views, leading to unintended server-side POST requests or other unauthorized backend interactions. Successful exploitation requires an attacker to have access to the target GitHub Enterprise Server instance and to entice a privileged user to view crafted malicious content that includes conflicting HTML elements. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18.3, 3.17.9, 3.16.12, 3.15.16, and 3.14.21.

References

• https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.3
• https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.9
• https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.12
• https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.16
• https://docs.github.com/en/enterprise-server@3.14/admin/release-notes#3.14.21