Could be a defect? Man that is dangerous, thank god you guys were alright. I can’t think of a reason an iPhone would do that. Man that is crazy.
My son was given an old, reconditioned iPhone by a relative which had a new battery in it.
After a couple of charges the screen started lifting so we put it to one side while deciding whether it was worth fixing.
The screen lifted some more and we decided to take it apart as son wanted to see what was inside.
As we were prying the back off, it got dropped and we heard a loud pop and the battery doubled in size exploding outwards. I imagine we were lucky it had no charge in it and did not start a fire!