Mantle Network (Bridge Contracts)

The accounting approach for deposits in `L1StandardBridge.sol` and burning and minting operations in `L2StandardBridge.sol` are not compatible with ERC-20 tokens that (but not limited to): - Have a transfer, minting, or burning fee - Are deflationary/inflationary (i.e. the balance of an account can change "arbitrarily", without a transfer operation) - Its L2 version unexpectedly reverts when minting, burning, or transferring - Its L2 version does not implement minting and burning operations properly (e.g. mints or burns more or fewer tokens than expected, leading to duplicate funds or issues when withdrawing from L2) - Implement blocklists <br> Currently, the system allows anyone to deploy a compatible token in L2 and link it to an L1 token. Users are responsible for ensuring that the ERC-20 L2 token is correct and that its behavior is not in the abovementioned list. **Interacting with a non-compatible token will block user funds in `L1StandardBridge.sol`.**

Although a test suite in the repository exists, it is from the original Optimism repository. The Mantle team stated that they do not have unit tests at this moment that cover the Mantle bridge contracts.

`L1StandardBridge.initialize()` is a public function with no access control. If `L1StandardBridge` is deployed behind a proxy, anyone can initialize the implementation contract by calling `initialize()` with arbitrary values. Although this does not affect the functionality of the project, it may open possible phishing or social engineering attacks (e.g. an attacker can try to impersonate Mantle). If the contract is not deployed using a proxy, there is a possibility of front-running. After contract deployment, an attacker can call `initialize()`, needing to deploy the contract again.

Every Solidity file specifies in the header a version number of the format `pragma solidity (^)0.8.*`. The caret (`^`) before the version number implies an unlocked pragma, meaning that the compiler will use the specified version _and above_, hence the term "unlocked".