.md

Context: PolygonL1Switchboard, PolygonL2Switchboard NativeSwitchboardBase.sol

Severity: Medium

Description: 

In NativeSwitchboardBase.sol, the receivePacket function is used to record the Merkle root for a given packet ID emitted by a remote switchboard

     */
    function receivePacket(
        bytes32 packetId_,
        bytes32 root_
    ) external onlyRemoteSwitchboard {
        packetIdToRoot[packetId_] = root_;
        emit RootReceived(packetId_, root_);
    }

However, in both PolygonL1 and L2 switchboards, the modifier is overriden but always returns true.

   * @notice This modifier overrides the onlyRemoteSwitchboard modifier in the NativeSwitchboardBase contract
     */
    modifier onlyRemoteSwitchboard() override {
        require(true, "ONLY_FX_CHILD");

        _;
    }

This means that the function receivePacket can be called by anyone and any packet id could be rewritten to arbitrary value.

Estimated to have a severity of Medium because it fits in: Damage to users/protocol due to griefing

Recommendation:

Use the modifier as intended so it serves its purpose to restrict access.