magic_number_hack.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract MagicNum {
    address public solver;

    constructor() {}

    function setSolver(address _solver) public {
        solver = _solver;
    }
}

contract MagicNumberHack {
    address public target;

    constructor(address _target) payable {
        target = _target;
    }

    function hack() external {
        bytes memory code = "\x60\x0a\x60\x0c\x60\x00\x39\x60\x0a\x60\x00\xf3\x60\x2a\x60\x80\x52\x60\x20\x60\x80\xf3";
        address solver;
        assembly {
            solver := create(0, add(code, 0x20), mload(code))
        }
        MagicNum(target).setSolver(solver);
    }
}