It's been posted in other sections, and a lot of you have asked (including myself) about it...well here's the official announcement.
Hi everyone,
Just a quick note to let you know we recently pushed out a hotfix to address a few issues in MP and Nazi Zombies.
* MP Castle is secure – you can no longer get under the map
* Proactively addressed a few potential exploitable MP locations in other maps
* Addressed all known Nazi Zombie exploits to-date
Regards,
-JD