iOS bug causes Messages crash, iPhone reboot

From 9to5mac:

A newly found bug surrounding iOS and Messages has emerged this evening that causes the app to continuously crash when a certain text is received. If the text is received while the phone is on the lock screen, it also causes your iPhone to reboot without any notice or explanation.

And:

Since the characters strand is so specific, most people should never accidentally experience the crashing. Anyone who does experience the crashing was likely singled out on purpose as a target.

If someone does send you that offending string, just send yourself a new text. You can tell Siri:

Send text to xxxx

Replace xxxx with your name, then respond to Siri with specifics when prompted for the phone number to use and the content of the text.

Hopefully, the Messages team is hard at work on a fix.