This is a strange and potentially game-breaking bug, initiated via a very unusual process. View the attached images in the correct order (1, 2, then 3) to see how it is done. In summary (though I strongly recommend you view the images), the bug is created while wearing boots with +Infinity and -Infinity (yes, infinity. Not some obscenely large number, not the ∞ character, but an actual infinite attribute, which is possible in Minecraft with some work and/or modification) Armor Toughness attribute, and taking normally-fatal damage while wearing them. This initiates a strange state. View the images to see what I'm talking about.