Styjun

I am loading an <iframe> in my HTML page and trying to access the elements within it using Javascript, but when I try to execute my code, I get the following error:

SecurityError: Blocked a frame with origin "http://www.<domain>.com" from accessing a cross-origin frame.

Can you please help me to find a solution so that I can access the elements in the frame?

I am using this code for testing, but in vain:

$(document).ready(function() 
 var iframeWindow = document.getElementById("my-iframe-id").contentWindow;

 iframeWindow.addEventListener("load", function() );
);

Same-origin policy

^{Not to be confused with CORS!}

You can't access an <iframe> with different origin using JavaScript, it would be a huge security flaw if you could do it. For the same-origin policy browsers block scripts trying to access a frame with a different origin.

Origin is considered different if at least one of the following parts of the address isn't maintained:

<protocol>://<hostname>:<port>/path/to/page.html 

Protocol, hostname and port must be the same of your domain, if you want to access a frame.

Examples

Here's what would happen trying to access the following URLs from http://www.example.com/home/index.html

URL RESULT 
http://www.example.com/home/other.html -> Success 
http://www.example.com/dir/inner/another.php -> Success 
http://www.example.com:80 -> Success (default port for HTTP) 
http://www.example.com:2251 -> Failure: different port 
http://data.example.com/dir/other.html -> Failure: different hostname 
https://www.example.com/home/index.html.html -> Failure: different protocol 
ftp://www.example.com:21 -> Failure: different protocol & port 
https://google.com/search?q=james+bond -> Failure: different hostname & protocol 

Workaround

Even though same-origin policy blocks scripts from accessing the content of sites with a different origin, if you own both the pages, you can work around this problem using window.postMessage and its relative message event to send messages between the two pages, like this:

• 
  

  In your main page:

  
  
  

  var frame = document.getElementById('your-frame-id'); 
  
  frame.contentWindow.postMessage(/*any variable or object here*/, '*'); 
  

  
  


• 
  

  In your <iframe> (contained in the main page):

  
  
  

  window.addEventListener('message', function(event) 
  
   // IMPORTANT: Check the origin of the data! 
   if (~event.origin.indexOf('http://yoursite.com')) 
   // The data has been sent from your site 
  
   // The data sent with postMessage is stored in event.data 
   console.log(event.data); 
   else 
   // The data hasn't been sent from your site! 
   // Be careful! Do not use it. 
   return; 
   
  ); 
  

  
  

This method can be applied in both directions, creating a listener in the main page too, and receiving responses from the frame. The same logic can also be implemented in pop-ups and basically any new window generated by the main page (e.g. using window.open()) as well, without any difference.

Disabling same-origin policy in your browser

There already are some good answers about this topic (I just found them googling), so, for the browsers where this is possible, I'll link the relative answer. However, please remember that disabling the same-origin policy (or the CORS) will only affect your browser. Also, running a browser with same-origin security settings disabled grants any website access to cross-origin resources, so it's very unsafe and should be done for development purposes only.

• Google Chrome


• Mozilla Firefox


• Apple Safari: not possible, only CORS.


• Opera: not possible.


• Microsoft Edge: not possible.


• Microsoft Internet Explorer: not possible, only CORS.

Complementing Marco Bonelli's answer: the best current way of interacting between frames/iframes is using window.postMessage, supported by all browsers

Check the domain's web server for http://www.<domain>.com configuration for X-Frame-Options
It is a security feature designed to prevent clickJacking attacks,

How Does clickJacking work?

1. The evil page looks exactly like the victim page.


2. Then it tricked users to enter their username and password.

Technically the evil has an iframe with the source to the victim page.

<html>
 <iframe src='victim_domain.com'/>
 <input id="username" type="text" style="display: none;/>
 <input id="password" type="text" style="display: none;/>
 <script>
 //some JS code that click jacking the user username and input from inside the iframe...
 <script/>
<html>

How the security feature work

If you want to prevent web server request to be rendered within an iframe add the x-frame-options

X-Frame-Options DENY

The options are:

1. SAMEORIGIN //allow only to my own domain render my HTML inside an iframe.


2. DENY //do not allow my HTML to be rendered inside any iframe


3. "ALLOW-FROM https://example.com/" //allow specific domain to render my HTML inside an iframe

This is IIS config example:

 <httpProtocol>
 <customHeaders>
 <add name="X-Frame-Options" value="SAMEORIGIN" />
 </customHeaders>
 </httpProtocol>

The solution to the question

If the web server activated the security feature it may cause a client-side SecurityError as it should.

For me i wanted to implement a 2-way handshake, meaning:

- the parent window will load faster then the iframe

- the iframe should talk to the parent window as soon as its ready

- the parent is ready to receive the iframe message and replay

this code is used to set white label in the iframe using [CSS custom property]

code:
iframe

$(function() 
 window.onload = function() 
 // create listener
 function receiveMessage(e) 
 document.documentElement.style.setProperty('--header_bg', e.data.wl.header_bg);
 document.documentElement.style.setProperty('--header_text', e.data.wl.header_text);
 document.documentElement.style.setProperty('--button_bg', e.data.wl.button_bg);
 //alert(e.data.data.header_bg);
 
 window.addEventListener('message', receiveMessage);
 // call parent
 parent.postMessage("GetWhiteLabel","*");
 
);

parent

$(function() 
 // create listener
 var eventMethod = window.addEventListener ? "addEventListener" : "attachEvent";
 var eventer = window[eventMethod];
 var messageEvent = eventMethod == "attachEvent" ? "onmessage" : "message";
 eventer(messageEvent, function (e) 
 // replay to child (iframe) 
 document.getElementById('wrapper-iframe').contentWindow.postMessage(
 
 event_id: 'white_label_message',
 wl: 
 header_bg: $('#Header').css('background-color'),
 header_text: $('#Header .HoverMenu a').css('color'),
 button_bg: $('#Header .HoverMenu a').css('background-color')
 
 ,
 '*'
 );
 , false);
);

naturally you can limit the origins and the text, this is easy-to-work-with code

i found this examlpe to be helpful:
[Cross-Domain Messaging With postMessage]