A major bug found in the latest version of iOS causes phones to crash when they receive a special/malicious text message.
If someone sends you the below string of Arabic characters via SMS or iMessage, it can cause the Messages app to stop working and can take down the phone entirely if it appears in a lock screen notification.
لُلُصّبُلُلصّبُررً ॣ ॣh ॣ ॣ 冗
The bug appears to be related to how iOS processes Unicode text for banner notifications using the CoreText API.
It affects iOS 7 and iOS 8 right now and the only fix is to send a photo or piece of text to the original sender using the share sheet in another app.
➤ iPhone security vulnerability [Reddit]