The 2.18 series release notes contain important changes in this release series.

Security Fixes

• HIGH: The legacy avatar upgrade functionality was vulnerable to a Server-Side Request Forgery (SSRF) vulnerability when fetching image content from third-party avatar services. This could allow an attacker to make GET requests to internal services reachable from the GitHub Enterprise deployment.
• LOW: The script-src: 'unsafe-inline' CSP header was applied to all paths for Enterprise Manager.
• Packages have been updated to the latest security versions.

Bug Fixes

• Promoting a replica in an active HA environment could fail to properly apply configuration changes and remove a pre-flight check holding page.
• A race condition could occur when a replica node was rebooted, preventing the internal VPN from starting correctly.
• MySQL replication lag could rise significantly on high traffic instances during times of peak user activity.

Changes

• The Google Accounts Daemon and google_set_hostname DHCP hook are now disabled on Google Cloud Platform images.
• GitHub Enterprise Server is now available in the eu-north-1 AWS region.
• MySQL database seeding progress is reported during replication setup and recorded in the configuration log.

Known Issues

• On a freshly set up GitHub Enterprise Server without any users, an attacker could create the first admin user.
• Custom firewall rules are not maintained during an upgrade.
• Subversion (SVN) checkout may timeout while the repository data cache is being built. In most cases, subsequent Subversion checkout attempts will succeed.
• Git LFS tracked files uploaded through the web interface are incorrectly added directly to the repository.
• Issues cannot be closed if they contain a permalink to a blob in the same repository where the file path is longer than 255 characters.
• When using Let's Encrypt with a new installation, an error can occur when creating a new Let's Encrypt account.
• When "Users can search GitHub.com" is enabled with GitHub Connect, issues in private and internal repositories are not included in GitHub.com search results.
• Security alerts are not reported when pushing to a repository on the command line. (updated 2020-06-23)

Thanks!

The GitHub Team