Pro WoW player risks it all by using a bug to get a 4% damage increase in world first race before getting caught on stream

pcgamer.com:

A World of Warcraft player racing to be one of the first in the world to clear the MMO's latest raid quietly used a bug to squeeze out a tiny bit more damage on the Nexus-Princess Ky’veza boss. It only gave him around a 4% damage increase, but it could've been enough to finish a fight his guild had been attempting for days in the world first Nerub-ar Palace race.

The bug could be called an exploit depending on who you ask because it takes a very deliberate method to use it. Team Liquid raider Imfiredup used a spell called Splinterstorm that is normally supposed to automatically shoot towards your current target. If you didn't have a valid enemy target, however, the spell simply wouldn't work properly and continue building up the debuff until you did.

By targeting his own character and using WoW's alternative 'focus' targeting system to cast his other spells (using macros) at the boss, Imfiredup could build up over 200 stacks of the debuff without Splinterstorm automatically seeking it out. Then, all he had to do was click on the boss to unleash a massive explosion of damage at once.

It would be one thing if everyone was openly using the bug, but Imfiredup appeared to be trying to hide it on the Liquid stream. Instead of having his normal target health bar on the right side of his custom UI like most players, Imfiredup put the focus target's there, which many think was to cover up that he was actually targeting himself most of the fight for the bug to work.

WoW mod developer Luckyone posted a screenshot that explains what's going on. You can just barely see the blue circle underneath Imfiredup's character that indicates he's targeting himself, despite having the boss health bar where your main target would usually be. In the middle of a fight where hundreds of spell effects are going off from the boss and other players, you wouldn't notice this unless you knew what to look for.

Explaining the @LiquidGuild mage bug mentioned in the @Gingitv tweet in this picture