title: How to make postMessage applicable to all subdomains
body: <p>In <code>window.postMessage</code> second attribute specifies domain to which my message can be sent. Is there any way to specify that it is applicable to all subdomains.</p>
  
  <p>Things tried:</p>
  
  <pre><code>iframe.contentWindow.postMessage('The message to send.','http://*.wordpress.com');
  iframe.contentWindow.postMessage('The message to send.','http://wordpress.com');
  </code></pre>