The bug was caused by an integer overflow error. When calculating the total value of transaction outputs, the software used a 32-bit integer variable that exceeded its maximum value due to a large output value.
That's incorrect - it was always 64 bit. In fact, the two outputs which this transaction created were very close to INT64_MAX, which is 0x7fffffffffffffff, or 9223372036854775807. The two outputs were 92,233,720,368.54277039 each.
The bug was fixed in Bitcoin Core version 0.3.10.
The bug was actually fixed in a standalone patch Satoshi released within a few hours. Version 0.3.10 was the first full version to include this patch.
The fix involved modifying the code to use a larger data type (64-bit integer) for handling transaction values, preventing similar overflow issues in the future.
No, it didn't. As vv181 has pointed out, it just implemented sanity checks.
The incident did not lead to the creation of any extra bitcoins.
This is also wrong. The incident absolutely led to the creation of 184 billion bitcoin. These bitcoin no longer exist because the chain was re-orged to remove them, but they were still created in the first place.
The 0.5 BTC from the malicious transaction never became a permanent part of the blockchain and did not affect the current state of the Bitcoin network.
Sorry, but this is wrong yet again. That 0.5 BTC absolutely still exists. It is the 0.5 BTC on this address -
https://mempool.space/address/17TASsYPbdLrJo3UDxFfCMu5GXmxFwVZSW. This is the input which was used in the value overflow incident, which now still exists as an unspent UTXO since the value overflow transaction was re-orged out. It has not moved since, but it is still there and still completely valid to be spent in the future.
because I would love to know some technical facts about what actually happened.
What happened is someone created a transaction which spent the 0.5 BTC I linked to above. They created two outputs in this transaction, both for 92,233,720,368.54277039 BTC. At the time, part of the way the software checked if the transaction was valid was to ensure the fee (i.e. the sum of the inputs minus the sum of the outputs) was equal or greater than zero. If you had higher outputs than inputs, then when you subtracted them your fee would be negative, and so the transaction would be rejected.
However, when the software added the value of the two outputs together, they overflowed and became negative. So then when the software subtracted this negative number from the 0.5 BTC, it ended up with a positive number, which passed the check for the fee to be positive. And so the transaction was allowed.
