Borderlands 2 developer Gearbox has confirmed that their update to address the issues with data loss is available now. It deals with the hack causing players to lose their save file.
The game is now safe to play with those not on your buddies list with this exploit now gone. In addition, Gearbox has added additional security to prevent the possibility of it happening again.
Xbox 360 players should get the update the next time they start the game up, as long as they are connected to Xbox Live.