Apple has been forced to pull an update to iOS for iPhones, iPads and iPod Touch after it was found to disable security features and mobile connectivity on a large number of handsets.
The update was issued through iOS on Wednesday to fix various bugs and reinstate access to HealthKit, its new fitness software, for compatible apps.
But after huge numbers of users found that their phones were not connecting to networks after the update, Apple was forced to act.
It has now pulled the software and users are being told to reset their phones to reconnect to their networks.
If you didn't specifically update to 8.0.1 today then you don't need to take any actionj - you're fine.
Apple told The Verge:
"We are actively investigating these reports and will provide information as quickly as we can. In the meantime we have pulled back the iOS 8.0.1 update."
Fortunately it's possible to downgrade back to iOS 8 - follow the instructions here to do just that.