From a security perspective, what measures were applied when using iFrame and PostMessage?

When using iFrame and PostMessage, it is important to consider several security measures:

• Source verification: always check the event.origin property in the message handler and accept messages only from trusted domains.

• Specifying the target window: when sending a message via postMessage, use the second parameter — the target origin — to prevent the message from being sent to an unintended recipient.

• Minimize trust: transmit only necessary data, avoid sending sensitive information.

• Content Security Policy (CSP): restrict iFrame loading to trusted sources only.

Example of message verification:

window.addEventListener('message', (event) => {
  if (event.origin !== 'https://trusted-domain.com') {
    return; // Ignore messages from untrusted sources
  }
  // Process the message
});

// Sending a message
iframe.contentWindow.postMessage(message, 'https://trusted-domain.com');