An Online Pandemic — World of Warcraft: Corrupted Blood Incident

Jack Leavey
2 min readFeb 21, 2023
Unforeseen uses of a debuff lead to mass player deaths.

One of the more famous glitches in videogame history derives from one of the largest MMOs: World of Warcraft. Taking place in September of 2005, the community was devastated when an exploit was found involving the corrupted blood debuff from the newly added Zul’Gurab Raid. This raid was a big deal: it was the first 20 person raid in WoW history. Unfortunately, an oversight in one of the abilities in the boss battle led to disaster.

Debuff: Corrupted Blood

Hakkar, the final boss of the raid, applies a debuff known as “corrupted blood” to players during the battle. This debuff is cleansed from the player when the leave the dungeon instance, confining it to the raid itself. However, debuffs can be applied to pets, and pets do NOT cleanse debuffs when they exit the dungeon.

This lead to the debuff making its way into the greater realms of WoW. This debuff dealt several hundred damage per second to players infected, and would spread based on physical proximity to other players. While high level players could survive the debuff, it would instantly kill lower level players. Furthermore, it was possible to spread the debuff back and forth between two players, meaning the only way to avoid inevitable death was to isolate away from other players and avoid contact.

While some of the player base attempted to avoid spreading the plague, others reveled in the destruction they were causing, and would intentionally seek out other players to continue spreading the debuff. This glitch was so potent that it changed how WoW was played for almost a month; players seldom went on quests and were instead interacting with the plague system as an unintended side effect from the developers.

As Ferreira described it: “In this sense, a glitch is both the product of malfunction and artificial creation.” (xCoAx2020-Ferreira.pdf, pg 113). This glitch is particular was born of a malfunction on the part of the developers, but it only became a phenomenon when the player base artificially created the issue by intentionally spreading it. The incident could not have occured without both parties’ actions regarding the glitch itself.

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Jack Leavey

I am a software engineer with years of experience branching into game development, specifically in Unity. Follow along for guides on creating game mechanics!