Mitigation Confirmed for M-01

[code423n4]

Mitigation of M-01: Fully Alleviated

The sponsor implemented the recommended course of action to address this exhibit, introducing the notBlacklisted modifier to the KUMABondToken::approve call and thus preventing approvals to be performed on behalf of a blacklisted owner. A snippet of the contract with the remediated code showcased can be found below:

/**
 * @dev See {IERC721-approve}.
 * @dev Adds the following conditions to the call :
 *      - Caller and spender must not be blacklisted
 *      - Contract must not be paused
 */
function approve(address to, uint256 tokenId)
    public
    override(ERC721, IERC721)
    whenNotPaused
    notBlacklisted(to)
    notBlacklisted(msg.sender)

    /** 
     * MITIGATION BLOCK OF M-01 START
     */

    notBlacklisted(ownerOf(tokenId))

    /** 
     * MITIGATION BLOCK OF M-01 END
     */
{
    address owner = ERC721.ownerOf(tokenId);

    if (to == owner) {
        revert Errors.ERC721_APPROVAL_TO_CURRENT_OWNER();
    }
    if (_msgSender() != owner && !isApprovedForAll(owner, _msgSender())) {
        revert Errors.ERC721_APPROVE_CALLER_IS_NOT_TOKEN_OWNER_OR_APPROVED_FOR_ALL();
    }
    _approve(to, tokenId);
}

As such, it is no longer possible to approve an NFT asset on behalf of a blacklisted owner. As an optimization, I would recommend the blacklist validation to be performed within the function's body as presently, the evaluation of ERC721::ownerOf is performed twice redundantly (once for the modifier and once in the function's body).

An accompanying test was introduced to the codebase's KUMABondToken.t.sol file that ensures a BLACKLIST_ACCOUNT_IS_BLACKLISTED error is yielded with the correct address argument.

[c4-judge]

GalloDaSballo marked the issue as satisfactory