A significant bug has been discovered in FaceTime and is currently spreading virally over social media. The bug lets you call anyone with FaceTime, and immediately hear the audio coming from their phone before the person on the other end has accepted or rejected the incoming call. Apple has taken Group FaceTime offline in an attempt to address the issue in the interim. Apple says the issue will be addressed in a software update later this week 9to5Mac has reproduced the bug with an iPhone X calling a iPhone XR, but it is believed to affect any iOS devices running iOS 12.1 or later.”]
Source: https://9to5mac.com/2019/01/28/facetime-bug-hear-audio/