The message, which contains characters and words in different languages, causes iPhones, iPads, Apple watches and Macs to shut down if it's sent via a direct message or public mention on Twitter's iOS app.
The issue through the iOS messaging apps was discovered after tests by the Guardian and security researcher Mikko Hypponen.
When sent through the Twitter app no lasting damage was caused, however if sent via Snapchat the message could not be cleared, the Guardian found.
Apple has issued a "workaround" to stop the bug crashing devices and is working on a permanent fix for the issue. However, it's unclear whether the same instructions would work on the message if sent via Twitter or Snapchat rather than iMessage.
- Ask Siri to "read unread messages."
- Use Siri to reply to the malicious message. After you reply, you'll be able to open Messages again.
- In Messages, swipe left to delete the entire thread. Or tap and hold the malicious message, tap "More", and delete the message from the thread.