Apple iPhones around the world are being attacked by a small "text bomb" message that causes the devices to freeze and eventually crash.
First appearing on Discord and Telegram groups earlier this week (via The Verge), the bug can cause this problem even if the message just pops up in your notifications. You can see what it does to an iPhone running the latest live version of iOS (iOS 13.4.1) in YouTuber EverythingApplePro's tweet below.
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The craziest iOS crash text bug 💀 pic.twitter.com/29LJPb67WPApril 23, 2020
The original version of this text bomb used an Italian-flag emoji as part of the message, but this isn't actually necessary for the bomb to work.
How does the iOS "text bomb" work?
While I'm certainly no coding expert, this is a surface-level explanation of what is causing this message to be such a tricky customer.
It seems to come down to the use of Sindhi characters in the text. Sindhi is a language spoken in Pakistan and India, which can be written in several scripts, including the Perso-Arabic and Devanagari (Hindi) alphabets. This particular bug seems to involve Perso-Arabic characters.
A feature of Arabic-based writing systems is the ability to type other characters by stacking smaller script elements (called diacritics) on top of and below the main characters in a sentence, which is what the tiny symbols trailing out of the message bubbles are.
Having this message show up in your notifications means that iOS needs to shorten the message with an ellipsis (a "...").
Abbreviating this mass of different characters means that some of the letters change position or size unexpectedly, which then causes your phone to process them incorrectly, leading to it trying to access a non-existent part of your device's memory, which finally causes a malfunction like a freeze or crash.
This explanation is based on similar text bombs from the past which have used Arabic characters, such as 2015's "Effective Power" bug.
How to fix iOS "text bomb" freeze or crash
While it's alarming to see your phone suddenly freeze or switch itself off, there's not actually any damage being caused to your phone. Your iPhone will probably reset itself soon after the crash, which is an annoying waste of your time but is a pretty mild consequence in the grand scheme of things.
If your phone doesn't reset itself, you can force it to do so by pressing the volume up button, then the volume down button, and then holding the side button until the Apple logo appears.
How to avoid iOS "text bomb"
The chances that you'll come across this bug in the wild are quite rare. What's more likely is that a mischievous friend of yours will try and send you this message.
To avoid the problem, turn off the notifications for your messaging apps via Settings -> Notifications, then select the apps in question and set the top Allow Notifications slider to the off position.
Apple is working on the problem, since the most recent beta for iOS 13.4.5 doesn't seem to suffer from the bug (via 9to5Mac (opens in new tab)). Hopefully it will be rushing out an update in the next few days which will then solve the problem once you've downloaded it, allowing you to turn your notifications back on safely.