In functions `mintSingleERC20Capsule(...)` and `mintMultiERC20Capsule(...)`, there are no checks to determine whether the pre- and post-deposit ERC20 amounts are the same. This can be an issue when special, deflationary ERC20 contracts burn some percentage of the tokens in every token transfer. Such behaviour in `CapsuleMinter` is contrary to the intent in the whitepaper, which states "the Capsule Protocol ensures that the exact same amount of token deposited is found at the contract post-mint". The code of the function `mintMultiERC20Capsule(...)` is presented below: ``` function mintMultiERC20Capsule( address _capsule, address[] memory _tokens, uint256[] memory _amounts, string memory _uri, address _receiver ) external payable nonReentrant onlyCollectionMinter(_capsule) checkStatus { uint256 tokensLength = _tokens.length; uint256 amountsLength = _amounts.length; require(tokensLength <= TOKEN_TYPE_LIMIT, Errors.INVALID_TOKEN_ARRAY_LENGTH); require(amountsLength <= TOKEN_TYPE_LIMIT, Errors.INVALID_AMOUNT_ARRAY_LENGTH); require(tokensLength == amountsLength, Errors.LENGTH_MISMATCH); // get the current top counter uint256 _id = ICapsule(_capsule).counter(); // Some tokens, like USDT, may have a transfer fee, so we want to record actual transfer amount uint256[] memory _actualAmounts = new uint256[](amountsLength); // loop assumes that the token address and amount is mapped to the same index in both arrays // meaning: the user is sending _amounts[0] of _tokens[0] for (uint256 i; i < tokensLength; i++) { address _token = _tokens[i]; uint256 _amount = _amounts[i]; require(_amount != 0, Errors.INVALID_TOKEN_AMOUNT); require(_token != address(0), Errors.INVALID_TOKEN_ADDRESS); // transfer tokens from caller to contract _actualAmounts[i] = _depositToken(IERC20(_token), _msgSender(), _amount); } // then add user data into the contract (tie Capsule NFT to input): multiERC20Capsule[_capsule][_id].tokenAddresses = _tokens; multiERC20Capsule[_capsule][_id].tokenAmounts = _actualAmounts; // lastly, mint the Capsule NFT ICapsule(_capsule).mint(_receiver, _uri); emit MultiERC20CapsuleMinted(_receiver, _capsule, _tokens, _amounts, _uri); } ```

The code of the function `mintSingleERC20Capsule(...)` (without inline comments) is presented below: ``` function mintSingleERC20Capsule( address _capsule, address _token, uint256 _amount, string memory _uri, address _receiver ) external payable nonReentrant onlyCollectionMinter(_capsule) checkStatus { require(_amount != 0, Errors.INVALID_TOKEN_AMOUNT); require(_token != address(0), Errors.INVALID_TOKEN_ADDRESS); // get the current top counter uint256 id = ICapsule(_capsule).counter(); // transfer tokens from caller to contract uint256 _actualAmount = _depositToken(IERC20(_token), _msgSender(), _amount); // then, add user data into the contract (tie NFT to value): // - set the ID of the Capsule NFT at counter to map to the passed in tokenAddress // - set the ID of the Capsule NFT at counter to map to the passed in tokenAmount singleERC20Capsule[_capsule][id].tokenAddress = _token; singleERC20Capsule[_capsule][id].tokenAmount = _actualAmount; // lastly, mint the Capsule NFT (minted at the current counter (obtained above as id)) ICapsule(_capsule).mint(_receiver, _uri); emit SingleERC20CapsuleMinted(_receiver, _capsule, _token, _amount, _uri); } ```