When sent a text chat with the offending string, it permanently crashes the iPhone when the user attempts to read it. The bug means that the user cannot open their chat history with the person who sent the message without crashing their iPhone.
The message cannot be cleared, but other messages can be sent to and received from other contacts. Apple issued recovery instructions for its Messages app, which involves using Siri to reply to a message allowing users to then delete that conversation.
A similar recovery method can use the Photos app to send a picture to a contact and gain access to the message history so it can be deleted.
The company said that a fix for the bug via a software update will be provided. You can disable notifications to protect your device from the mischievous text, but that will not prevent Snapchat and other third-party apps from being disabled.