A new bug discovered on iOS 11 allows a user to send a specific character that will block the iPhone with a risk of bootloop and the app in which it is used.
The bug was discovered by MobileWorld and was also confirmed by The Verge. The problem occurs when a particular Indian character is received or used, which effectively blocks the app used and the entire operating system, forcing the user to restart the iPhone. What you see above is just the character that, for some strange reason, crashes iOS. By the way, if this character is received in the Messages app, it will not be easy to restore the use of the app itself.
In fact, at the moment, it seems that the only way to restore access to messages is to ask the person who sent the message to delete the thread that contained the wrong character. The same happens if the message is sent to other messaging apps such as WhatsApp or Telegram: in this case, every time you try to reopen the app, it will go to lock and it will close immediately. In general, the problem occurs in any app in which the character in question is received or pasted.
Also, if the offending character is shown in a push notification, it will be the entire iOS Springboard. As reported by MobileWorld, in this case the advice is DOES NOT RESTART the iPhone, because otherwise you would risk a continuous bootloop. The advice is to wait for the Springboard to restart itself after a few attempts.
Be careful and do not share this special character with your contacts, because the risk is to block important apps like Messages or WhatsApp or, worse, to bootloop the device, forcing the user to a restore in DFU.
The bug affects not only iOS, but also WatchOS and macOS. From the tests carried out, iOS 11.3 seems to have already corrected this problem (the final version should come out in spring)