Shop - The Ethernaut - Writeup

Fri, 05 Jun 2026 00:00:00 +0000

Сan you get the item from the shop for less than the price asked?

This is the code of the challenge’s contract:

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

interface IBuyer {
  function price() external view returns (uint256);
}

contract Shop {
  uint256 public price = 100;
  bool public isSold;

  function buy() public {
    IBuyer _buyer = IBuyer(msg.sender);

    if (_buyer.price() >= price && !isSold) {
      isSold = true;
      price = _buyer.price();
    }
  }
}

Basically, the first call of the price() function must return >= 100. The second call made to price() must return < 100. We control the logic of the buyer, so this should be pretty easy.

View Functions on manbolq's Blog

Shop - The Ethernaut - Writeup