Peter Bright over at ArsTechnica:
Their bogus chargers—which do, incidentally, charge the phone—contain small computers instead of mere transformers. The iPhone treats these computers just as it does any other computer, but instead of just charging, it responds to USB commands. It turns out that the iPhone is very trusting of USB-attached computers; as long as the iPhone is unlocked (if only for a split second) while attached to a USB host, then the host has considerable control over the iPhone.
Makes you think twice about where you should be buying your adapters. May want to stay away from less reputable merchants. You may pay more for a 1st party Apple adapter, but at least you know what you're getting.