In Aug 2010, a bug in Bitcoin’s source code was exploited by someone who to this day remains anonymous. The anomaly was in block # 74638 and quickly spotted on the Bitcoin Talk forum by Jeff Garzik.
The bug that caused this “value overflow incident” resulted in 184 billion Bitcoins being created. Ultimately a fix, to change the consensus rules that rejected output value overflow transactions was released in just five hours. There was no significant impact on the price of Bitcoin.