Elevator

Reach the top floor of the building by exploiting the interface.

Vulnerable Code

Analyze the Solidity code below to find the vulnerability.

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

interface Building {
  function isLastFloor(uint) external returns (bool);
}


contract Elevator {
  bool public top;
  uint public floor;

  function goTo(uint _floor) public {
    Building building = Building(msg.sender); // Treats caller as the Building

    if (! building.isLastFloor(_floor)) {
      floor = _floor;
      top = building.isLastFloor(floor);
    }
  }
}

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Explain the vulnerability and how to exploit it.

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Hints (3)

Just a little peak

Hint 1

Hint 2

Hint 3

Explanation

Discomfort = Learning

Elevator

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