August 5, 2010 — the date that marked the beginning of the era of understanding vulnerabilities in cryptocurrencies. On this day, the first fork in Bitcoin's history occurred, triggered by a critical bug in the code that temporarily undermined one of the fundamental principles of the network — the emission limit of 21 million coins.
Block #74,638 recorded an anomalous transaction that created 184,467,440,737.09551616 BTC. The cause was an integer overflow in the source code of Bitcoin Core. The vulnerability allowed the system to accept an incorrectly large sum when adding the input and output values of the transaction.
This instantly put the entire project at risk. The very concept of Bitcoin as a deflationary and predictable asset depended on the strict limit of 21 million BTC. Violating this limit could have destroyed trust in the system at its earliest stages.
Satoshi Nakamoto, the creator of Bitcoin, personally responded to the issue. Just 3 hours after the incident, a patch was released — Bitcoin Core version 0.3.10, which included:
Fixed a bug with overflow;
Added validation checks for input and output sums;
Transactions that violated the emission limit began to be rejected.
After the update, the network temporarily split into two versions:
The chain with the bug contained block 74,638 with 'fake' coins.
The chain with the fix did not accept this block and rolled back to the previous one (74,637).
Miners faced a choice: continue working with the bug or switch to the safe version. Thanks to the coordinated response of the community, most nodes and miners switched to the fixed version.
The basic principle of Bitcoin was triggered — Longest Chain Rule: the longest and 'heaviest' chain (with the most cumulative work) is recognized as true. After a few hours, the chain with the bug lost support and was ultimately discarded.
This was the only case in Bitcoin's history where a block was manually rolled back and completely excluded from history.
The technical bug of 2010 was not a planned event. But by May 2011, Bitcoin Core v0.3.19 was released, which included backward incompatibility — a full hard fork:
Signature verification was changed.
Support for new transaction formats was added.
This was the first official protocol fork, however, it was accepted by nearly all miners, and there was no network split.
The truly loud and politicized split only occurred in August 2017, when a separate cryptocurrency — Bitcoin Cash (BCH) — was created due to disagreements over block size (1 MB vs 8 MB).
This event marked a new era — when forks began to be used not only as a means of code update but also as a mechanism for ideological and economic differentiation within the crypto community.
This was a test of Bitcoin's resilience. It passed thanks to quick decision-making and the involvement of its creator.
The bug showed that trust in code cannot be absolute, especially in the early stages.
This case laid the groundwork for the future architecture of decentralized updates: minimizing unilateral control, testing, multi-signature solutions.
From this moment on, it became clear: blockchain is not just code. It is a living socio-technical organism, the resilience of which depends not only on algorithms but also on the consensus of its participants.
