On August 15, 2010, an unknown attacker exploited a flaw in the Bitcoin protocol known as a "value overflow" bug in block 74638. The bug allowed the creation of 184 billion BTC—far beyond the 21 million supply cap hardcoded into Bitcoin’s rules. This exploit occurred because the code did not correctly check for overflow errors when verifying transactions. Specifically, an attacker was able to send an output with a value so high that it "wrapped around" into a negative number, tricking the software into accepting the transaction.
Immediate Response
Satoshi Nakamoto and other core developers quickly responded.
Within hours, they released a new version (0.3.10) of the Bitcoin software that fixed the vulnerability.
The community agreed to hard fork the blockchain at block 74638, effectively rolling back the invalid transaction and restoring the legitimate chain.
Impact at the Time
At that time, Bitcoin was still a niche experiment.
The price of BTC was less than $0.10, and there were only a few thousand users.
The rapid and transparent response restored confidence among early adopters.
It set a precedent for community coordination and emergency responses.
