It involves Face ID and the fact that it can have more than just your face enrolled. Face ID offers a super-fast and convenient way to unlock modern iPhones and iPads, and it’s super secure. But it’s only as secure as your passcode. If someone secretly knows your passcode (maybe they’ve shoulder-surfed you to get it), they could add their face to your iPhone or iPad and could be unlocking your device with the same ease that you’re unlocking it. Must read: Check your iPhone for compromised passwords… NOW! OK, so how do you tell if someone else’s face is enrolled with your Face ID? Tap Settings > Face ID & Passcode and enter your passcode. If you see the option to Set Up an Alternative Appearance, then there’s only one face enrolled, and you’re OK. However, if that option is not visible, there are two faces enrolled (or perhaps you enrolled your face twice). If this is that case, and you’ve not set up your device so someone else can access it, tap on Reset Face ID and go through the enrollment process again (it takes seconds). I also recommend – highly recommend – that you change your passcode. To do this tap Settings > Face ID & Passcode, and enter your passcode, and then tap Change Passcode. It’s quick to check and quick to fix. As to whose face was set up as the alternative appearance, there’s no way to know (unless you go pointing your locked iPhone at people and see if it unlocks) because the face isn’t stored, only a digital representation, and this is locked away in Apple’s Secure Enclave chip. I recommend installing iVerify. It’s a very handy security app that’s packed with information on how to make your iPhone or iPad more secure.