A new string of characters has been discovered that can crash iPhone, iPad, Apple Watch, and even Mac devices.
The bug affects apps like Messages, Mail, and others, and it's triggered when a certain string of characters is sent to your device. Discovered on Reddit (via MacRumors), the string includes the Italian flag emoji and characters from the Sindhi language. You can see an example of this particular string below.
The problem is that the crashes are caused by notifications, so there's not much you can do to stop people from sending the malicious string to you. You can turn off notifications to try and avoid your apps from crashing while we wait for a fix from Apple.
Apple hasn't yet acknowledged this bug, so it's unclear when a fix might be released. Two years ago a similar bug was discovered that could cause your iPhone to crash when it received a specific character from the Telugu language. Apple ended up releasing an update to fix the bug four days later, so hopefully we'll see a fix for this bug in a similar timeframe or perhaps even faster.
UPDATE: A video from EverythingApplePro shows that the Italian flag emoji isn't necessary to cause your phone to crash. When the notification comes in, you'll no longer be able to leave the app you're in or lock your device and eventually it'll crash.