Some XBOX Live users have violated the online gaming platform s code of conduct by using a malicious application that allowed them to permanently kill off the characters of other players in the popular Borderlands 2 video game. The bug does not affect players on the PC or PlayStation 3. Users can avoid having their characters eliminated by playing only with trusted friends in private online sessions. A fix has been submitted to Microsoft and a fix will be released as soon as possible, but players can still save and quit from the pause menu while characters are still alive.
Source: https://threatpost.com/trouble-borderlands-2-players-103012/77166/