The Standard

Summary

A user can burn all "minted" EUROs and not be able to pay protocol's fee

Vulnerability Details

In the mint function, fee and amount minted are added together and stored in "minted".

   minted = minted + _amount + fee;

https://github.com/Cyfrin/2023-12-the-standard/blob/91132936cb09ef9bf82f38ab1106346e2ad60f91/contracts/SmartVaultV3.sol#L163-L163

Based on the ifMinted modifer, "minted" can either be greater than or equal to _amount:

modifier ifMinted(uint256 _amount) {
require(minted >= _amount, "err-insuff-minted");
_;
}
https://github.com/Cyfrin/2023-12-the-standard/blob/91132936cb09ef9bf82f38ab1106346e2ad60f91/contracts/SmartVaultV3.sol#L53-L56

Now in the burn function, a user can enter all the "minted" into the "_amount" parameter and this will pass. Since "_amount" is equal to "minted". Then, the burn function will burn all this minted amount from the user.

EUROs.burn(msg.sender, _amount);

The next line of code after the above is transferring fee from the user to the protocol:

    IERC20(address(EUROs)).safeTransferFrom(msg.sender, ISmartVaultManagerV3(manager).protocol(), fee);

This will be impossible and revert since the user has burnt all minted EUROs.

Impact

A user won't be able to pay protocol's fee after burning all minted EUROs.

Tools Used

Manual review

Recommendations

Fee should be removed from _amount before burning