Microsoft has begun pushing out the first update since NoDo to help thwart fake certificates that are currently circulating the web.



From Neowin.net:

The update which is described as being a critical fix, according to WMpoweruser, corrects an issue related to fraudulent third party digital certificates. Microsoft is issuing the patch in the name of security to help protect end users from fake certificates. Microsoft pushed out the update with little noise and the update will change the OS build to 7392.

  Microsoft begins pushing out certificate update to WP7