While it would be exceedingly difficult for somebody who's not a family member to bypass the Face ID of your iPhone X (for details on that, click here) it's very, very possible that somebody within your family, be it a sibling or kid, could hack their way onto your phone just by looking at it. This, of course, would represent a problem when your kid is either curious, irresponsible (especially with apps that cost money), or just a rambunctious little a-hole.
Previously, Apple has admitted that this was a security feature that could be tricked by kids younger than the age of 13, or by twins. Not much you can do in those instances, especially with the latter group. However, a new video was posted onto YouTube that shows there could be a possibility for family members who don't really look that much like you (I mean, right? Look at the video above) to get into your phone without your consent.
That video shows Sana Sherwani and her 10-year-old son, Ammar, both being able to access her phone due to technology that is, perhaps, not as great as previously advertised. Furthermore, according to a pretty in-depth report on this family's situation that was published by WIRED on Tuesday morning, Ammar was able to unlock his mom's phone on the first try. In addition to that, he was also able to get into his dad's phone, but only in one out of several attempts.
If this is a problem you may have (or think you may have) WIRED notes that a potential workaround would be taking a picture of your face in different lighting. That's what Sana did with her phone, though Ammar was able to get back in after they re-registered for a third time in a dimmer room.
Apple says that Face ID is a more secure method than Touch ID, though this would probably be a video they'd have preferred was never made (especially since it's trending). Worth noting is that Ammar's young age could've potentially played a role in getting into his mom's phone, as Apple said kids younger than 13 with "undeveloped facial features" might cause issues with this.
Anyway, looks like there's still some bugs to iron out. While it's not clear how widespread this issue is, Attaullah Malik, the kid's dad, has a recommendation for parents who may not want family members rifling through their phones. "You should probably try it with every member of your family and see who can access it." Good advice.
You can read the WIRED report in its entirety right here.