https://phys.org/news/2019-02-apple-facetime-eavesdropping.html

The bug enabled interlopers to turn an iPhone into a live microphone while using Group FaceTime.

Apple turned off the group chat feature last week, after a 14-year-old boy in Tucson, Arizona, discovered the flaw. The teenager, Grant Thompson, and his mother said they unsuccessfully tried to contact the company about the problem for more than a week.