Quote from: cr1776 on Today at 12:30:31 PM

Double spend has a well defined meaning, so BitMEXResearch saying there was a double spend is wrong too. If double spend means the second one above then every RBF is a double spend and their never was a "double spend" problem to solve.

in this case there was a block reorganization, so a confirmed transaction (1 confirmation) was dropped from the blockchain and a conflicting transaction was mined instead. that doesn't apply to every RBF transaction.

Quote from: cr1776 on Today at 12:30:31 PM

I agree that some people have used "double spend" incorrectly when they want to say "attempted double spend" or "attempt to replace one low fee transaction with another by spending the same bitcoins again in a higher fee transaction."

i generally agree but i don't wanna get into an argument about semantics.

fundamentally, a 1-block reorganization is very normal---so if everyone is putting all their trust in 1 confirmation, then we have a problem. this specific transaction may not have been malicious, but that doesn't mean these threats are not real:

Quote

Blockchain reorganization attack

Also called alternative history attack. This attack has a chance to work even if the merchant waits for some confirmations, but requires relatively high hashrate and risk of significant expense in wasted electricity to the attacking miner.

The attacker submits to the merchant/network a transaction which pays the merchant, while privately mining an alternative blockchain fork in which a fraudulent double-spending transaction is included instead. After waiting for n confirmations, the merchant sends the product. If the attacker happened to find more than n blocks at this point, he releases his fork and regains his coins; otherwise, he can try to continue extending his fork with the hope of being able to catch up with the network.

https://en.bitcoin.it/wiki/Irreversible_Transactions#Blockchain_reorganization_attack

maybe peoples' confidence in 1 confirmation should be shaken a little more...