The patch, which was announced last month, prevents data loss tied to an external application sabotaging user accounts.
Some users complained of lost save files when playing against strangers in public sessions. Infected users, meanwhile, continued to spread the virus - which was tied to a "hardcore mode" - by playing online.
The update is available now, and can be downloaded by activating the game while connected to Xbox Live Arcade.
Released in September, Borderlands 2 was the biggest-selling launch of the year until the release of FIFA 13.
The first of four pieces of campaign DLC, titled 'Captain Scarlett and her Pirate's Booty', was released last month.
It can be purchased individually, or with the discounted Borderlands 2 season pass.
Each pack costs $9.99 (£6.30) on PC and PS3 and 800 Microsoft Points (£6.80 / $10) on the Xbox 360.
The Season Pass, meanwhile, can be picked up for $29.99 (£18.90) on PS3 and PC, and 2400 Microsoft Points (£20 / $30) on Xbox 360.
> Read Digital Spy's Borderlands 2 review
Watch the launch trailer for Borderlands 2 below: