Telephone - The Ethernaut - Writeup

Wed, 22 Apr 2026 00:00:00 +0000

Claim ownership of the contract below to complete this level.

This is the contract’s code:

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

contract Telephone {
    address public owner;

    constructor() {
        owner = msg.sender;
    }

    function changeOwner(address _owner) public {
        if (tx.origin != msg.sender) {
            owner = _owner;
        }
    }
}

In order to change the owner of the contract, we need to call the changeOwner function, in a way that tx.origin != msg.sender. In this Ethereum Stackexchange question, its difference is discussed. It is simple, though: the EVM allows contracts to call functions on another contracts. Then, we could have a chain of calls like this:

Tx.origin on manbolq's Blog

Telephone - The Ethernaut - Writeup