Turn and move, someone discovers some crazy character string or just a specific character in a language capable of locking the iPhone. See some examples below:
Today, another one was discovered and again by the YouTube channel EverythingApplePro:
The bug called ?Black dot? because of its origin: the string (including an emoji from a black ball) was sent by WhatsApp and crashed devices running the Android operating system. The iOS version is a little different, but it includes the black ball emoji, not to mention that the purpose is exactly the same, to lock the device.
A layman (like me) may not see it, but strings contains thousands of hidden and invisible Unicode characters, exactly what causes the device's CPU to panic while trying to process everything. In the case of iOS, the sequence will only crash the system if sent by the Messages app (Messages).
I didn't test it here, but Benjamin Mayo (from 9to5Mac) stated that when copying the sequence on his Mac (in order to write the article on the subject), the system also went into trouble. Thus, it makes sense to imagine that the problem also affects watchOS and tvOS systems.
Speaking specifically of iOS, the bug affects both version 11.3 (.1) and version 11.4, which is in the testing phase. However, now that the information has spread, Apple is quite capable of fixing the problem in the next beta build.
If someone sends you such a string and your iPhone crashes, you just need to find a way out of the Messages app screen that shows those characters. It is possible, for example, to force the exit and use 3D Touch on the app icon to open a new message; then just go back to the main list with all the messages and delete that conversation with the damn string. If you have other Apple devices (like iPad or Mac, properly synced by iCloud), you can also delete the message from it that it disappears on the iPhone.