Fee Update

In the MerkleVester contract the _handleClaimFee function does not refund any native value sent if the claim fee is assigned to 0.

Because of this ETH may become trapped in the MerkleVester contract without being able to be rescued as there is no native recovery method.

Consider reverting if the claim fee is 0 and the msg.value is nonzero.

With the setClaimFee function the fee setter may assign any claimFee value. Therefore the fee setter may frontrun users who are attempting to withdraw their allocations and raise the fee to higher than the value that was sent so that the withdrawal reverts.

Claims may also be trivially prevented by assigning a claim fee which is extremely high. Thus no user will be able to afford to claim their allocation. This can serve as a way to revoke allocations for those which should be non-revokable.

Consider assigning either a hard cap for the claim fee or an immutable cap which can be assigned at construction time.

In the MerkleVester contract upon withdrawing the native fee is sent to the feeCollector. However if the feeCollector is assigned to a contract which cannot accept ether then all withdrawals will be DoS’d.

Be aware of this risk and clearly document it for users of Magna’s MerkleVester.