https://www.cnbc.com/2019/02/07/apple-facetime-bug-fixed-in-iphone-update.html

Apple just released iOS 12.1.4 which includes a fix for a group FaceTime bug that let people eavesdrop on conversations even if they never answered a call.

The bug went viral last week after a 14-year old discovered that, while group FaceTiming with friends on his iPhone, he was able to hear someone who hadn't picked up when he called. Apple acknowledged the bug and apologized.