New job, instant emergency patch

Final Fantasy 14's beastmaster class launched on September 8, and Square Enix pushed emergency maintenance the same day to kill a bug it shipped with.

The exact trigger

If a player's character left the area from a connection loss at the precise moment their pet used a weapon skill that healed its master, the server could go down.

“the server may crash”

Not your client, the server

This one skipped the player's own game entirely and took out the machine everyone else was playing on. The conditions are narrow, but nothing about them is accidental.

An ethernet cable is the exploit

Losing connection on cue just means unplugging. That turns a fringe race condition into something any player could fire off deliberately, which is why the fix could not wait.

“it's easily replicated with a cheeky pull of one's ethernet cable”

Limited jobs draw a crowd

Beastmaster is a limited job like blue mage: locked out of main story and endgame, loaded with odd abilities. Everyone piles in at launch, so a server-killer would have spread fast.

Square Enix has form here

Last year players got disconnected for listing an auction house item in one specific zone priced between 44,442 and 49,087 gil. It won PC Gamer's award for most specific MMO bug fix.

“between 44,442 gil and 49,087 gil”