Can Iframes Access the Parent Page's URL Across Subdomains?

Accessing Parent URL from an Iframe

Despite residing on the same domain, the inability to retrieve the parent page's URL via an iframe often arises when the subdomains differ. This behavior prompts the question: does cross-site scripting (XSS) extend to subdomains?

Understanding the Restriction

The answer lies in the browser's security measures. Even though the main page and iframe share a domain (e.g., www.mysite.com), the subdomain distinction (e.g., www vs. qa-www) falls under different "origins." This separation prevents malicious actors from accessing and manipulating data across different websites and their subdomains.

Alternative Solution

While direct access to the parent page's URL is restricted due to XSS concerns, an alternative approach can provide the necessary information. To obtain the URL of the parent page (i.e., the browser URL), the following code can be used:

var url = (window.location != window.parent.location)
            ? document.referrer
            : document.location.href;

Note:

• window.parent.location is accessible and avoids security errors.
• document.referrer may not always return the containing document's URL if an external source influenced the iframe's location.
• document.location refers to the current document (the iframe) and its URL. It provides the desired parent URL if the iframe and parent share the same href.

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