First Flight #4: Boss Bridge

Summary

There is a slight risk of temporary DoS in depositTokensToL2().

Vulnerability Details

Funds only move out when the off-chain service picks up events emitted by the contract by submitting signed withdrawal transactions.
A well funded attacker could donate tokens to make the token balance of the contract reach DEPOSIT_LIMIT, effectively preventing future deposits since no events is emitted for donations and thus, the off-chain service will not move funds out. This is only temporary until an admin with access to the off-chain service private key sends a manual transaction to move funds out.

Impact

DoS of future deposits.

Tools Used

Manual review.

Recommendations

Use state variables to do the accounting instead of relying on token.balanceOf(address(vault)).