how I discovered the bug (go down to see the actual steps to reproduce):

I was playing on my hardcore world, when I noticed there was a lot of monsters outside, because it was night. I went to sleep, and when I woke up, I went outside, and noticed that zombies and skeletons were bouncing around like a crazy rabbit, while on fire. I went closer to see what was going on, and then a zombie on fire punched me and i catched fire too. I started taking knockback from the fire, and jumping in many directions (as effect that the fire damage isn't caused in only one side, with determined knockback direction, this also occurs with snowballs fired by dispensers, making mobs jump around crazy).

hopefully, I survived from the fire to tell this history!

Steps to Reproduce:
1- Simply get yourself or a mob on fire
2-see the magic!