There is a Unicode crash bug occur could cause iPhone, iPad or Apple Watch that runs with iOS 8 to reboot or crash, as receiving a message containing the specific string of Unicode characters. This is due to iOS difficulty of rendering them making iOS device restarts.
This Unicode crash bug characters is
Powerلُلُصّبُلُلصّبُررً ॣ ॣh ॣ ॣ 冗
Contains a random mix of Arabic and other characters. Apple aware of an iMessage issue caused by a specific series of Unicode characters and will make a fix available in a software update.
In the meantime waiting Apple roll out update to fix this issue, we can follow this temporary solution to prevent your iPhone, iPad, or Apple Watch from being affected and should fix the notification crashes.
Unicode Crash Bug Solution For Jailbreak Users
Now a jailbreak developer (MohammadAG) seems faster than Apple rolled out Cydia tweak, Unicode Suppressorn which can fix the Unicode bug from crashing the iOS devices. Please install this tweak quickly if your iOS devices already jailbreak to avoid others sending this kind of Unicode to your iOS devices.
Open up Cydia app in your iOS devices, go to “Source” to add http://repo.cydro.us.
Now searching for Unicode Suppressorn and installed, then restart SpringBoard.
Your iPhone, iPad or Apple Watch will not crash again if someone sending Unicode characters through iMessage.