A couple of days ago a serious bug was discovered in iOS messages app that could cause your iPhone to restart.
Apple has confirmed this problem and posted a temporary solution on their website yesterday. Here's what you can do:
If Messages quits unexpectedly after you get a text with a specific string of charactersApple is aware of an iMessage issue caused by a specific series of unicode characters and we will make a fix available in a software update. Until the update is available, you can use these steps to re-open the Messages App.
- Ask Siri to "read unread messages."
- Use Siri to reply to the malicious message. After you reply, you'll be able to open Messages again.
- In Messages, swipe left to delete the entire thread. Or tap and hold the malicious message, tap More, and delete the message from the thread.