Apparently it was a bug that allowed this according to Techspot and it will be corrected in the big update.
One issue that is still under investigation is the high data usage some users are seeing with their Windows Phone 7 device. The BBC is saying that Microsoft has acknowledged the problem.
More stories are popping up, mostly in the US. Reports include phones transferring 30-50MB each day and 2-5MB per hour. That will eat into a 2GB monthly plan in a hurry. If you are roaming, that could eat into your wallet as well.
At least Microsoft has now started investigating the issue. Unless the fix turns out to be trivial, and that is assuming it is a problem with the phone itself, it is doubtful Microsoft can make the fix and properly test it internally and with the carriers and still make the pending update. That would actually be a good test of Microsoft's ability and willingness to release minor updates as needed without bundling them together into service pack style updates.