Information disclosure in GitHub Enterprise Server leading to private repository leakage

An authorization/sensitive information disclosure vulnerability was identified in GitHub Enterprise Server that allowed a fork to retain read access to an upstream repository after its visibility was changed to private. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.10.0 and was fixed in versions 3.9.4, 3.8.9, 3.7.16 and 3.6.18. This vulnerability was reported via the GitHub Bug Bounty program.