low.md

Use typed selector during encoding of executeCalls function

Instead of using abi.encodeWithSignature with the signature as a string, use the typed selector present in the ICrossChainExecutor interface to improve readability, resilience and be less error prone.

This is present in the relayers for Arbitrum and Optimism.

Example:

bytes memory _data = abi.encodeWithSelector(
  ICrossChainExecutor.executeCalls.selector,
  _nonce,
  _sender,
  _calls
);

Unused import in EthereumToPolygonRelayer.sol

The imported interface ICrossChainExecutor isn't used in the contract.

Check if msg.value is zero in calls to relayCalls

Although the interface for the relayCalls function requires a payable mutability modifier, the relayer implementation in all 3 cases (Optimism, Arbitrum, Polygon) doesn't use msg.value and doesn't forward it, making it unnecessary to transfer payments in calls to this function. Consider adding a check to revert if a transaction transfers ETH by mistake.