Borderlands 2 characters are safe from the nefarious plots of evil men, Xbox 360 owners are not afforded such a luxury.
"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 Studios community manager Chris Faylor said in a post on the developer's official forums.
While Gearbox and its "partners" work to resolve the Xbox-specific issue, it recommends avoiding public games with unknown players for the time being. Additionally, players should always Save & Quit before returning to the dashboard or powering down their Xbox, and if you find yourself kicked back to the main menu after death, select "Continue" immediately.
What destruction is actually involved in the exploit's sabotage is uncertain – anecdotal accounts on the forum report everything from wiped character progress to entirely deleted characters. We've reached out to Gearbox for clarification and will update with any new information we receive.
Update: Gearbox has informed us that a patch to exterminate the exploit has been submitted to Microsoft for approval and will be released "as soon as possible."