Before I get started, I just want to let everyone know that everything is okay, and -will- be taken care of, the map will be rolled back to the most recent backup (server restart), which was about 5 hours ago (2 PM EST).
What happened is there's an authentication glitch in Spigot (a custom server that most large server use) that is allowing people to login as any player. This same thing happened to multiple other large servers, we are not the only ones. We updated this, and it will not happen again.
We are all extremely sorry for what happened, but hopefully you all can understand.