The ecrecover() call here does not verify 0 < s < secp256k1.n  2 + 1.
This restriction was introduced Homestead (EIP-2), but left the precompile unchanged. Most libraries, such as OpenZeppelin, perform this check.
There does not seem to be an immediate risk in the current use cases, because an order can be verified only once and its hash is stored. These places are _validateBasicOrderAndUpdateStatus, _validateOrderAndUpdateStatus and validate.
Context: SignatureVerification.sol#L91
Perform the check.
