GitHub Host key verification failed

As I came into work this morning I went to pull from GitHub and hit the error:

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:randomchars.
Please contact your system administrator.
Add correct host key in /Users/username/.ssh/known_hosts to get rid of this message.
Offending RSA key in /Users/username/.ssh/known_hosts:1
Host key for github.com has changed and you have requested strict checking.
Host key verification failed.
fatal: Could not read from remote repository.

Turns out GitHub had discovered that GitHub.com’s RSA SSH private key was briefly exposed in a public GitHub repository and more details are in their announcement:

The fix was easy, and I just removed the “GitHub” line from .ssh/known_hosts so it was regenerated. But you can also follow along in that article for updating it manually.