Group FaceTime Bug
Apple has released iOS 12.1.4 to fix the group FaceTime privacy bug. I highly recommend updating to 12.1.4.
However, it will be interesting to see what happens when you try to use group FaceTime if you have not updated. Will group FaceTime be disabled for devices that have not updated? It does not seem likely that Apple would re-enable group FaceTime leaving older versions vulnerable to the bug. Let me know your experience in the comments.