robsware

The vulnerability is Improper Input Validation

html
<!-- Insert the vulnerable code into a short web application -->
<!DOCTYPE html>
<html>
<head>
  <title>Input Validation Example</title>
  <script src="vulnerable.js"></script>
</head>
<body>
  <input id="userNameInput" type="text" placeholder="Enter your name" />
  <button onclick="greetUser(userNameInput.value)">Greet</button>
</body>
</html>

javascript
// vulnerable code
function greetUser(userName) {
  alert('Hello, ' + userName + '!');
}

const userInputElement = document.getElementById('userNameInput');
const userName = userInputElement.value;
greetUser(userName);

javascript // vulnerable code function greetUser(userName) { alert('Hello, ' + userName + '!'); } const userInputElement = document.getElementById('userNameInput'); const userName = userInputElement.value; greetUser(userName); The vulnerability in the initial code is due to not validating or sanitizing the user input, which allows for potentially malicious content to be executed. The solution is to use a proper input validation and sanitization method, such as the `escapeHTML` function in the provided solution. This function creates a temporary DOM element and sets its textContent to the user input, which automatically escapes any potentially dangerous HTML entities. As a result, when the modified `greetUser` function uses `safeUserName`, it's guaranteed to be free from any potential threats.

javascript
// solution how to fix the vulnerable code
function escapeHTML(unsafeText) {
  const div = document.createElement('div');
  div.textContent = unsafeText;
  return div.innerHTML;
}

function greetUser(userName) {
  const safeUserName = escapeHTML(userName);
  alert('Hello, ' + safeUserName + '!');
}

const userInputElement = document.getElementById('userNameInput');
const userName = userInputElement.value;
greetUser(userName);