If it's a forceful opening and you're not holding the top tightly, then I imagine the top could launch upwards. I know from experience this can also happen if you put just a bit of boiling water in and seal it. The air expands under heat and will push the top out whilst you're unscrewing. A version of this top comes with a metal spoon & raised holder built in, providing some edges to hit you with and an extra projectile.