If you value your precious saved games in Borderlands 2 on Xbox 360, you'd best only play with those you trust. Playing online with those using a hacked exploit runs the risk of wiping your characters afterwards.
Eurogamer reports that using the "Graveyard" exploit, players can hack save files to access a hardcore mode left in the game. But, those playing online with someone who has enabled the hack have found their characters deleted. This has opened the way to griefing, which Gearbox has called "sabotage."
"Recently a few users have begun violating the Xbox Live Code of Conduct by using an external application to maliciously disrupt the experience and sabotage characters of legitimate Borderlands 2 players on Xbox 360," community manager Chris Faylor wrote on the game's forum. "Fortunately it's easy to avoid this scenario."
Faylor says that a patch has been submitted to Microsoft to fix the exploit, but in the meantime advises players to only play in non-public sessions with those they know and trust. If you're playing on the PC or PlayStation 3, you're in luck, as the bug doesn't impact you. He also advises using the Save and Quit option to be on the safe side, and if you find yourself in the main menu after dying, immediately select "Continue."
Finally, if you've been a victim or even simply seen suspicious behavior, Faylor asks players to submit feedback to Gearbox itself.