A newly discovered bug in Apple’s iOS mobile operating system lets iPhone users crash another user’s iPhone by just sending a tiny string of text characters in a message. The bug is related to the Messages app and the notification system used by iPhone and iPad devices. A string of particular Arabic characters used in the text message causes the iPhone to continuously crash when a certain text is received and reportedly in some cases causes the phone to reboot without notice. The string of characters is a very specific set of characters, and many have fallen victims to this new Unicode character bug.
Source: https://thehackernews.com/2015/05/this-simple-text-message-can-crash-and_26.html