Xbox 360 copies of Borderlands 2 have been hit by a malicious attack that is wiping player saves, developer Gearbox has announced.
A patch to fix the issue was submitted to Microsoft last week, but users report the problem is still ongoing.
The "Graveyard" exploit began when users hacked save files to access a Diablo 3-style hardcore mode left within the game's code by developers.
Users playing online with those who have the exploit enabled have unwittingly found their characters wiped forever when they have died.
Developer Gearbox has labelled the issue - now spreading across Xbox Live via unwitting players - as "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," Gearbox community manager Chris Faylor wrote last week on the game's official forum. "Fortunately it's easy to avoid this scenario.
"After extensive internal testing, an update to prevent this disruption has been submitted to Microsoft and will be released as soon as possible. Until then, concerned Xbox 360 players of Borderlands 2 should consider playing online with trusted individuals in non-public sessions. This does not affect players on PC or PlayStation 3."
Players are advised to exit their game sessions via the Save and Quit option from the in-game pause menu. Anyone finding themselves at the Borderlands 2 main menu after dying should immediately select Continue to resume playing.
"We ask that players report any suspicious behaviour in Borderlands 2 to email@example.com and provide as much details and documentation of their disrupted experience as possible to assist us in our investigation," Faylor concluded.
Gearbox has yet to respond to users who have already lost characters due to the exploit. It follows an earlier bug that wiped player Badass rankings.