Race Attack

From CryptoWiki

"A malicious actor creates two txs for the same digital asset. The tx they don’t want to succeed would be the one sent to the merchant’s address. The second tx, spending the digital asset to another wallet the malicious actor controls, would then be broadcast to a larger number of nodes on the network than the first (the more nodes controlled by the attacker, the better their chances of success). This is done so that the second tx has a better chance of being confirmed before the original one. The odds of a successful attack can be additionally increased through methods such as knowing the network topology. If successful, the attacker retains the original BTC sent but also ends up with the merchant’s services or products."