There was a new update for Call of Duty: Black Ops 2, developed by Treyarch and released in 2012. Obviously there is something going on as some in-game ads where changed and now contain a snapchat link. If you scan the code, Snapchat App is opened and shows the text: "callofduty is already your friend". Then you get a short and very strange video with a voice saying: "Listen only to the sound of my voice":
Activision and Treyarch haven't talked about this so far, but it looks like, it could be an viral marketing campaign for the next Call of Duty and as it's appearing in Call of Duty: Black Ops 2, the most obvious reason would be that Call of Duty: Black Ops 3 is the next CoD.