Team Avolition is a griefing group that commonly targets Minecraft-- I'm surprised that they're releasing the exploit at all.

From @notch: "We took down the auth servers until they've been fixed. I'll pass on everything I learn about what's going on, just woke up. ‪#groggy‬" "Also, in the future, if hackers could please not find exploits in the middle of the night on weekends, that would be great, mk?"