GitHub announced it detected unauthorized access in a few repositories used to plan and develop GitHub Desktop and Atom.

The company asked developers to update to the latest version of Desktop and the previous version of Atom before Feb. 2.

A compromised Personal Access Token associated with a machine account was used to clone repositories for atom, Desktop, and other GitHub-owned organizations.
The affected repositories did not contain customer data, but GitHub stored several code-signing certificates for use through Actions.
GitHub's investigation concluded that there was no risk to GitHub.com services, and no unauthorized changes were made to the projects.
GitHub shared a list of GitHub Desktop for Mac and Atom versions that will stop working on Feb. 2 in this post.