A serious error in the Apple FaceTime application allows users to listen to the people they are calling when they do not answer the call. In certain circumstances, the crash also allows callers to view the video of the person they are calling before answering.
The Guardian confirmed the existence of the bug, which was first reported by 9to5Mac.
The bug transforms the recipient's phone from a FaceTime call into a microphone while the call is still ringing. If the call recipient presses the power button on the side of the iPhone – an action normally used to mute or ignore an incoming call -, the phone will begin to transmit the video to the initial caller.
Apple did not immediately respond to a Guardian comment request. The company told Reuters it was aware of the problem and would launch a software update "later this week."
The bug comes amid growing concerns about the privacy of regulators around the world.
Apple has tried to distinguish itself from competing technology companies, such as Google and Facebook, because of its privacy history. In early January, the company posted a 13-story billboard in Las Vegas stating, "What happens on your iPhone, stays on your iPhone" during the Consumer Electronics Show.
Until Apple releases its software update, it seems the best way for iPhone users to protect their privacy is to disable FaceTime in their phone settings.