An iPhone user, Rocky, is reporting his iPhone got hot and exploded after it was upgraded to iOS 12.1.
Reports of exploding iPhone X phones have been rare and we have seen no other reports of iOS 12.1 causing similar behaviour.
The issue most likely relates to a defecting battery or charger. The user reportedly had the ipHone lugged into an official Apple charger and it had just restarted from finishing the update to iOS 12.1.
He has sent the iPhone off to Apple and is awaiting their diagnosis.