From callofduty.com:
This fix went live already and everyone on the two platforms should receive it. Fixes were the same for both platforms as well.
Source
Hey 360 gamers,
We are listening to you and we’ve been busy working on updates based on feedback from the community. We have already deployed a number of updates, and there will be many more to come. Stay tuned right here for all the latest info.
LIVE FIXES
3/17/11 (hotfix)
• Addressed several Zombies exploits.
• Addressed an exploit that allowed players to get outside of the designated map boundaries on Nuketown and Kowloon.
• Added "Mercenary" (TDM exclusive) playlist to MP.
• Disabled Split-Screen play in Mercenary playlists.
We are listening to you and we’ve been busy working on updates based on feedback from the community. We have already deployed a number of updates, and there will be many more to come. Stay tuned right here for all the latest info.
LIVE FIXES
3/17/11 (hotfix)
• Addressed several Zombies exploits.
• Addressed an exploit that allowed players to get outside of the designated map boundaries on Nuketown and Kowloon.
• Added "Mercenary" (TDM exclusive) playlist to MP.
• Disabled Split-Screen play in Mercenary playlists.
This fix went live already and everyone on the two platforms should receive it. Fixes were the same for both platforms as well.
Source