Someone can send the video link to your iPhone and, if you take the bait, it will gently slow your phone down over about 30 seconds until it stops and freezes altogether.
There's nothing you can do from there, apart from performing a hard reset on the phone. To do that you'll need to hold down the volume and power buttons for a few seconds.
Watch what you press
The top tip is avoid pressing on any suspicious looking video links you're sent, especially one entitled IMG_0942.mp4 from MacDigger.ru.
This may seem like a fun prank that shuts down your friend's phone with no consequences, but it’s currently uncertain where the glitch comes from and whether it will cause any long term damage to your phone.
It will work on devices running iOS 8 software and above, so it's not just current iPhone devices at risk.
It may also be something created by hackers to be able to get information from your phone, so try to avoid pressing the link if at all possible.
To see the glitch in action, check out the video from EverythingApplePro below.
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James is Managing Editor for Android Police. Previously, he was Senior Phones Editor for TechRadar, and he has covered smartphones and the mobile space for the best part of a decade bringing you news on all the big announcements from top manufacturers making mobile phones and other portable gadgets. James is often testing out and reviewing the latest and greatest mobile phones, smartwatches, tablets, virtual reality headsets, fitness trackers and more. He once fell over.