On September 27, the Marathon Digital miner mined an invalid block at height #809 478 on the Bitcoin mainnet due to a transaction-ordering issue.
It appears as if MARA had transactions in the wrong order.
The invalid block included this txn (A):https://t.co/IShJvlS8Ow
Spending an output from this txin (B):https://t.co/Z6BNJQqcYd
However, txin B was included in the block after txin A, therefore the block was invalid… https://t.co/rWC0mM8tyG
— BitMEX Research (@BitMEXResearch) September 27, 2023
Ultimately, other network participants rejected the invalid block because it attempted to spend funds from an unconfirmed transaction. The legitimate block #809 478 was mined by the Foundry USA pool.
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Later, Marathon representatives confirmed the incident, calling the event an unforeseen error.
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We can confirm that Marathon did mine an invalid block. We utilize a small portion of our hash rate to experiment with our development pool and research potential methods to optimize our operations. The error was the result of an unanticipated bug that came from one of our…
— Marathon Digital Holdings (NASDAQ: MARA) (@MarathonDH) September 27, 2023
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\”This experiment was by no means an attempt to alter Bitcoin Core in any way. Our team noticed the invalid block around the same time as the rest of the world, and we immediately fixed the bug. This incident, although unintentional, underscores the reliability of the network’s security, which rejected and eliminated the anomaly,\” the company said.
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Casa’s Chief Technology Officer Jameson Lopp joked that Bitcoin is an ‘impregnable fortress of verification that prevents double-spending’.
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In September, an unknown paid 1,982,108,632 satoshis ($510,750) as a fee for transferring 0.074 BTC (~$1,800). This was the largest dollar-value payment for a transaction confirmation.
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Later turned out, that the transfer was carried out by the infrastructure blockchain company Paxos. After the necessary checks, representatives of F2Pool returned 19.82 BTC to the firm.