Submitted by chaduke, also found by chaduke, Udsen, zero-idea, J4de, bin2chen, Aymen0909, Nyx, bart1e, anon, ladboy233, tapir, rvierdiiev, and mahdirostami
The flow bridgeProxy.deposit() -> L1WethBridge.deposit() -> Mailbox.requestL2Transaction() allows one to deposit WETH from L1 to L2.  However, when checking the deposit limit for a particular depositor, Mailbox.requestL2Transaction() checks the limit of msg.sender, which is the address of L1WethBridge.
https://github.com/code-423n4/2023-10-zksync/blob/1fb4649b612fac7b4ee613df6f6b7d921ddd6b0d/code/contracts/ethereum/contracts/zksync/facets/Mailbox.sol#L236-L273
As a result, when the limit of the bridge is reached, nobody can deposit anymore, even though their limit is not reached yet. As a result, sooner or later, nobody will be able to use Zksync to deposit weth to L2 from L1.
POC:
The following test file is a modification of the test file: zksync/code/contracts/ethereum/test/foundry/unit/concrete/Bridge/L1WethBridge/Deposit.t.sol. The test function is test_DepositExceedLimit().
Please run the following command under zksync/code/contracts/ethereum:
forge test --match-test test_DepositExceedLimit -vv
The following line has been commented out to skip the check of merkle root:
https://github.com/code-423n4/2023-10-zksync/blob/1fb4649b612fac7b4ee613df6f6b7d921ddd6b0d/code/contracts/ethereum/contracts/zksync/facets/Mailbox.sol#L142
Foundry, VScode
Check the limit of the real depositor instead of the limit for the L1WethBridge.
Math
miladpiri (zkSync) confirmed, but disagreed with severity and commented:
Alex the Entreprenerd (judge) decreased severity to Medium and commented:
