Hover and be immune to knockback and damage

Essentially, when you are on a server, any server, if you press f11 to window the game, then press escape to go to the menu, and finally right click on the top white bar at the top, your character will float, be immune to knockback and damage. 

As is shown in the video below, as long as I am holding right-click on the top bar, the character cannot move and I have tested it with my friends, I cannot take damage.