Within seconds the price of ETH crashed from ~$320 to as low as $0.10. While the price recovered quickly, the rapid price movement caused many traders to experience margin calls or stop loss orders, resulting in potentially severe losses.
While many initially thought the flash crash was the result of nefarious work, GDAX eventually confirmed that there was no indication of wrongdoing or account takeover.
Instead, the flash crash was the result of someone placing a multi-million-dollar sell order at market price, meaning ETH would change hands at whatever price bidders were currently offering until the entire order was filled – no matter how much lower the price was than the current price of ETH.
Filling this order caused ETH prices to instantly slip 30% to $224 – which in turn caused 800 stop loss orders and margin liquidations, which further drove the price down, to as low at $0.10.