It has been reported that BitMEX’s ForkMonitor noted that “multiple blocks were produced at height 666833.”
For anyone interested, here are the details we have for the transactions in question. Winning transaction (In block 666833):https://t.co/LCHaR2P2vF Losing conflicting transaction (In the stale block):https://t.co/kzbGnfmkq7 https://t.co/wZKbkQv14i — BitMEX Research (@BitMEXResearch) January 20, 2021
Soon after that, BitMEX Research attributed the orphaned block to an RBF transaction, which is where an unconfirmed transaction is replaced with a new transfer paying a higher fee.
ForkMonitor has since updated its advice to say:
“No (RBF) bumps have been detected.”
Twitter-user and BSV’s Australian advocate Eli Afram noted that the “mixed messages” from BitMEX Research, asserting the double-spent transaction should be cause for concern despite its small value:
“So it appears an actual Double-Spend has occurred on BTC… Not an RBF (replace-by-fee), but an actual double spend. A mere 22USD… but – this could have been 22million.”
Likewise, Satoshi Nakamoto’s Bitcoin Whitepaper is credited with having solved the double-spend problem in 2009.
Thus, the challenge of ensuring that a decentralized network can autonomously verify that the same coins have not been transferred more than once had stymied earlier attempts at digital cash.