UI misrepresentation of granted permissions in GitHub Enterprise Server leading to unauthorized access to user

Summary

A UI misrepresentation vulnerability was identified in GitHub Enterprise Server that allowed more permissions to be granted during a GitHub App's user-authorization web flow than was displayed to the user during approval. To exploit this vulnerability, an attacker would need to create a GitHub App on the instance and have a user authorize the application through the web authentication flow. All permissions being granted would properly be shown during the first authorization, but if the user later updated the set of repositories the app was installed on after the GitHub App had configured additional user-level permissions, those additional permissions would not be displayed, leading to more permissions being granted than the user potentially intended. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.3 and was fixed in versions 3.2.5, 3.1.13, 3.0.21. This vulnerability was reported via the GitHub Bug Bounty program.