After a player dies, if a creeper is in its ignition phase, it will still explode when the player is on the death screen.
Reproduction in Single-player world
spawn a creeper
set off its ignition without flint and steel
run the command /kill
Provided that the player died close enough to the creeper for it to keep exploding, it will explode. It is very likely that this will cause a loss of the player’s items in a normal singleplayer world.
I’m almost certain this is intended, the world keeps ticking until the player is fully dead.
Edit: I only tested with igniting the creeper with a flint and steel. I understand the argument that if a creeper hasn’t been forcibly ignited it should refrain from exploding if there are no living targets in range, so in that sense the classification of this as a valid bug makes sense.