Microsoft has found the culprit in the Windows Phone 7 issue of the mysterious data transfer happening without the users knowledge. Turns out, it was a third party application doing all the transfer. Of course, all fingers were pointed at Microsoft for the fault of the problem.

We have determined that a third-party solution commonly accessed from Windows Phones is configured in a manner that potentially causes larger than expected data downloads. We are in contact with the third party to assist them in making the necessary fixes, and are also pursuing potential workarounds to address the configuration issue in case those are needed. At this point in our investigation, we believe this is responsible for most of the reported incidents.