From Ghandi:

The emergency TU that went live at 2am PST was to combat the recent wave of hack and mod attacks. We had previously released a hot-fix that prevented the spread of these virally through joining public matches. However, malicious individuals were sadly still using other propagation vectors to disseminate hacks, including one that reset a player's rank.

This TU has tightened our security on these vectors. To be safe while we monitor the situation please continue to IGNORE friend invites from anyone you do not know.

Anyone that has suffered from a rank reset please contact Activision CS with your GamerTag. We shall be reverting all victims to the rank they attained pre attack.

We are taking all available measures to prevent future hacks of this nature. We take the sanctity of the game experience very seriously.

Please PM me or BanCandy if you still experience hacks in the wild. The sooner we hear about them the sooner they'll be eradicated.

Cheers,

G IH A IN ID II