QA Report

[code423n4]

L01 Missing != address(0) checks for Immutable Addresses

I recommend adding a address(0) check in the constructor when setting immutable addresses.
Executor.sol#L48

L02 SafeApprove is deprecated

As per Open Zepplin safeApprove should only be used when setting initial allowance or reseting to zero. safeIncreaseAllowance should be used instead.
AssetLogic.sol#L347

N01 Open Todos

Recommend removing open todos before deploying contracts
BridgeFacet.sol#L492
BridgeFacet.sol#L579
BridgeFacet.sol#L1027
Executor.sol#L7
LibConnextStorage.sol#L303

N02 Incomplete Natspec

AssetFacet.sol#L130 - missing @param _stableSwapPool
BaseConnextFacet.sol#L113 - missing @return
BridgeFacet.sol#L626 - missing @return
BridgeFacet.sol#L744 - missing @return
BridgeFacet.sol#L913 - missing @param _message
PortalFacet.sol#L79 - missing @param _transferId
RoutersFacet.sol#L130 - missing @param cananonicalId
StableSwapFacet.sol#L251 - missing @param amountIn, @param minAmountOut, @ param deadline, @return
StableSwapFacet.sol#L278 - missing @param amountIn, @param minAmountOut, @ param deadline, @return
AssetLogic.sol#L223 - missing @param _maxIn
AssetLogic.sol#L259 - missing @param _slippageTol
AssetLogic.sol#L301 - missing @param _maxIn
LibConnextStorage.sol#L72 - missing @param routerSignatures
LibConnextStorage.sol#L90- missing @param approvedForPortalRouters
SwapUtils.sol#L171 - missing @param totalSupply
SwapUtils.sol#L480 - missing @param balances
SwapUtils.sol#L511 - missing @param balances
SwapUtils.sol#L541 - missing @param self