Submitted by kyliek, also found by cccz
https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L45
https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/schain/tokens/ERC20OnChain.sol#L49-L50
https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/mainnet/DepositBoxes/DepositBoxERC20.sol#L95
https://github.com/skalenetwork/ima-c4-audit/blob/11d6a6ae5bf16af552edd75183791375e501915f/contracts/schain/tokens/ERC20OnChain.sol#L60-L63
Anyone on Schain that is able to mint more tokens, other than the mint action from postMessage in tokenManagerERC20 by bridging tokens over, can potentially drain the locked tokens in transferredAmount in depositBoxERC20 on mainnet by calling exit with the same amount of tokens in transferredAmount[schainHash][token].
This will trap other users funds on sChain and lost those funds on mainnet to the malicious attacker.
An example of proof of concept using ERC20OnChian is given below. This case may seem to be special as the deployer of the clone contract is malicious.  However, this is a potential risk that generalises to other custom contracts with any mint functionality.
Disable minting function to be called directly in ERC20OnChain. Only allow minting when bridging tokens over.
cstrangedk (SKALE) disputed and commented:
GalloDaSballo (judge) decreased severity to Medium and commented:
