All of my servers had the administrator username and passwords reset.

All of my servers are version 10 and are in development so they are not exposed to public. I also have a version 9 server running in production which is public. All of the 10 servers never had a username saved, I came in this moring and all server had the username set to admin (locked in browser) and some random password. Any idea as to how all servers changed?

I was able to reset the development user/pass but I am at a loss as to how they were all changed. No network intrusion was found.