Karam Daoud discovered he could make a phone call to any number from a locked iPhone by exploiting the emergency calling function, meaning a thief could make phone calls -- including to premium and international numbers -- without ever unlocking the device.
The trick was implemented by tapping "Emergency," then dialing any number and rapidly tapping the call button until a blank screen with the Apple logo appeared.
“Once the black screen appeared, it was pretty clear that this is a bug,” said Daoud. “You can dial a number anywhere, any time.”
Staff at tech site Mashable said they were able to recreate the bug on older iPhones running iOS 7 (devices as old as the iPhone 4 were capable of running the software), but not the new iPhone 5s.
The new version of the software, iOS 7.0.2, was made to specifically address that issue, as spelled out in the update notice.