Several male models in the game seem to be missing a leg. The current lack-of-leg conspiracy is spreading even to certain NPCs, a fact I can attest to because I witnessed poor Harrison Jones with the same affliction in the vestibule to Zul'Aman. To be specific, the illness affects certain boot models, causing them to vanish entirely from the character's left leg. When the boots are removed, the leg assumes it's normal opacity.
Does this mean someone is infecting footwear with invisibility? Will we log in one day to find our heads too have disappeared? We will keep a close watch on this crisis and report to you whatever grizzly details we encounter. Let it be known that WoW Insider will not stand idly by while characters' limbs begin to disappear.