The bug is actually quite easy to pull off, and involves sending an Indian language (Telugu) character to an iPhone. Once the person receives the text, the iOS Springboard crashes. After that point, the Messages apps can no longer be opened, as it will continually crash while it attempts to load the "offending" character.
The only way to break out of the crash cycle with Messages is to have one of your contacts send you a "clean" text message, after which the Messages app will properly open. You are then free to delete the text that caused the mayhem in the first place.
What's interesting is that this Indian-language character bug affects a wide range of popular communications apps including Facebook Messenger, Gmail, Outlook, Twitter and WhatsApp. Even more, it's not just iOS that is affected; the character crashing also extends to the Apple Watch (which runs watchOS) and Macs (which run macOS). In the case of macOS, apps like Notes, Safari, and the App Store will continually crash after receiving a tainted text.
According to The Verge, the Apple seems to have fixed the problem in the currently available iOS 11.3 beta. So once iOS 11.3 is officially released next month, we should be freed from this latest software malady to afflict Apple devices.
When we last visited the world of Apple bugs, iOS devices were “taken out” with the ChaiOS text bomb, which exploited the operating system's penchant for preloading website links. The end result was that affected iOS devices would freeze, respring or reboot.
There's hope for the future, however. With iOS 12, Apple is reportedly doubling down on squashing bugs and improving performance across the board.