Bitcoin holders could face losses on the main chain if they try to sell coins created by a proposed fork tied to the controversial BIP-110 proposal. The issue stems from duplicate balances that may appear on both chains after a split, creating the impression that holders have received extra coins for free. Because both chains are expected to accept the same transactions at first, selling the forked asset could trigger a replay attack (a transaction copied onto another chain), causing the seller to also spend real Bitcoin on the main network. A developer said there is no built-in replay protection (a safeguard that blocks cross-chain transaction copying) at least until early September, and non-professional users should avoid moving Bitcoin during a potential fork period.