XCN Token (Base) - Audit

In the contract `OptimismMintableERC20`, the `_bridge` contract has authority over the functions shown in the diagram below. Any compromise to the `_bridge` contract may allow the hacker to take advantage of this authority and mint tokens to arbitrary addresses or burn tokens from arbitrary addresses .  The scope of the audit treats third party entities as black boxes and assumes their functional correctness. However, in the real world, third parties can be compromised and this may lead to lost or stolen assets. In addition, upgrades of third parties can possibly create severe impacts.