Fixing Uncaught DOMException: Blocked Frame Error in Javascript

If you're encountering the "Uncaught DOMException: Blocked a frame with origin" error in your Javascript code, don't worry - there are several solutions you can try to fix it.

├Źndice
  1. What is the Uncaught DOMException error?
  2. Solution 1: Use the postMessage() method
  3. Solution 2: Modify the content security policy (CSP)
  4. Solution 3: Use a server-side proxy

What is the Uncaught DOMException error?

The Uncaught DOMException error occurs when your Javascript code attempts to access content from a frame or window that has a different origin than the parent window. This is a security feature built into web browsers to prevent cross-site scripting (XSS) attacks.

Solution 1: Use the postMessage() method

The postMessage() method allows you to send messages between windows or frames with different origins. To fix the Uncaught DOMException error, you can use this method to pass data or execute functions between your parent window and the blocked frame.

<!-- Parent window -->
<script>
  const iframe = document.querySelector('iframe');
  iframe.contentWindow.postMessage('Hello from parent', 'https://blockedframe.com');
</script>

<!-- Blocked frame -->
<script>
  window.addEventListener('message', (event) => {
    if (event.origin === 'https://parentwindow.com') {
      console.log(event.data);
    }
  });
</script>

Solution 2: Modify the content security policy (CSP)

The content security policy (CSP) is a set of rules that control which resources can be loaded on a web page. By default, most web browsers block resources from different origins to prevent XSS attacks. However, you can modify the CSP to allow content from specific origins to be loaded.

To modify the CSP, you can add the following header to your web server configuration:

Content-Security-Policy: frame-ancestors https://parentwindow.com;

This allows the blocked frame to be loaded within the parent window.

Solution 3: Use a server-side proxy

If you don't have control over the blocked frame's origin, you can use a server-side proxy to fetch the content and serve it from the same origin as the parent window. This will bypass the CORS policy and prevent the Uncaught DOMException error.

To implement a server-side proxy, you can use a server-side language like PHP or Node.js to fetch the content from the blocked frame and serve it from your own server.

By using these solutions, you can fix the Uncaught DOMException: Blocked Frame Error in Javascript and prevent XSS attacks on your web page.

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