[skimbrel]

I presume this is not strictly a Rails problem.

You can check in things that shouldn't be checked in with any language/framework.

If you have done this, here's how to fix it: http://help.github.com/remove-sensitive-data/

[kevinpet]

Better is to change your security token and expire all sessions. Removing sensitive data should be seen as just a suggestion. Google never forgets.