There are two external entry points execute(ConduitBatch1155Transfer[] calldata batchTransfers) and executeWithBatch1155(ConduitTransfer[] calldata standardTransfers, ConduitBatch1155Transfer[] calldata batchTransfers) which trigger the internal _transfer(...) function. It works off this data structure:
The _transfer function only supports the ERC-20/ERC-721/ERC-1155 item types, where it ensures that amount == 1 for ERC-721, but allows identifier to be anything for ERC-20 transfers.
It could be:
This problem is similar to the SpentItem/ReceivedItem fields can be dirty and unused issue and can be triggered through that transaction, but since the Conduit is a general purpose feature and could be used and triggered by other contracts too.
We believe that can have severe risks in the future. But it is hard to argue about the severity of this currently due to lack of clarity on what kinds of applications would be built on top of conduits.
Context: Conduit.sol#L174, Conduit.sol#L52, Conduit.sol#L117
Insert check that item.identifier == 0 for ConduitItemType.ERC20.
