Bitcoin BIP-110 fork could expose holders to replay attacks 
Bitcoin developer Kevin Loaec warned holders against moving coins following a possible BIP-110 chain split, citing the risk of replay attacks. A split would create two transaction histories with the same balances at the point of separation. Anyone holding 10 BTC before the fork, for example, would initially control 10 coins on each resulting chain. This second balance may appear to offer free money if a buyer offers to purchase the BIP-110 coins. However, both networks could initially recognize the same signed transaction.
A buyer could copy the transaction used to transfer the forked coins and broadcast it on the main Bitcoin network. If accepted, the seller would transfer the same amount of real BTC to the buyer’s address. The attack would not give the buyer access to the holder’s entire wallet. Only the inputs included in the signed transaction would move, while transaction fees could be charged on both chains.
Loaec said large holders may be targeted first because a successful replay involving their wallets would produce a larger return. Holders who do not know how to separate the balances can avoid that risk by leaving their coins unmoved, as there would be no signed transaction to replay.
