Unexpected postMessage events

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In modern web apps, the window.postMessage() method is commonly used to enable secure communication between different origins. However, if not properly managed, the use of this method can lead to unintended behaviors.


The Pendo agent uses postMessage events for communication between different origins. If your app also uses postMessage events but doesn't properly distinguish between the postMessage events being generated by Pendo and those generated by your app, there's a risk of processing unintended postMessage events from the Pendo agent.

This can cause unexpected POST request errors because your application might be expecting a particular format or set of data that isn't present in the postMessage events from Pendo.


This solution is one example approach to securing your application. Consider implementing selective processing logic within your postMessage listener based on message origin and content.

  1. Include a unique token in your messages. Modify the sending part of your application to include a unique type field with a value like customerNamespace:MessageName.
  2. Validate incoming messages. Update your message event listener to check for the presence and value of this unique type field before processing any messages. Additionally, verify the origin and destination to ensure it matches your expected sender.

Here's an example implementation:

// Sending a message
window.postMessage({ type: 'customerNamespace:MessageName', data: yourData }, 'https://your-app.com');

// Listening for messages
window.addEventListener('message', function(event) {
  // Check the origin of the message
  if (event.origin !== 'https://your-app.com') return;

  // Check the type of the message
  if (event.data.type && event.data.type.startsWith('customerNamespace:')) {
    // Process the message

function handleMessage(data) {
  // Your custom message handling logic

While this article demonstrates a basic validation method, it's essential to adapt the security measures to fit the specific needs and security requirements of your application.

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