https://thenextweb.com/apple/2019/01/29/apple-temporarily-disables-group-facetime-to-fix-a-bug-that-lets-you-eavesdrop-on-your-contacts/

There was chaos on the internet late last night after 9to5Mac discovered a bug in Apple’s FaceTime video calling app that let you hear other person’s voice even before they answered your call. According to the report, a user running iOS 12.1 could potentially exploit the vulnerability to eavesdrop on others through a group FaceTime call.

What’s more, The Verge noted if the recipient ignored or dismissed the call using the power button, their video feed was streamed to the caller.