Why Does Google Prefix JSON Responses with `while(1);`?

Why Google Prefixes JSON Responses with while(1);

In response to the recent observation that Google appends while(1); to their JSON responses, users have speculated on its purpose.

The primary reason for this practice is to mitigate JSON hijacking, a vulnerability that allows third-party websites to access sensitive user data through cross-origin AJAX requests. By prepending while(1);, Google ensures that the JSON content cannot be accessed by websites on other domains.

This works by leveraging browser security measures that prohibit third-party websites from modifying global array methods. Thus, even if an attacker includes a script tag referencing the Google JSON URL, they cannot override array constructor or accessor methods, effectively blocking data access.

While this technique prevents JSON hijacking, it does not address cross-site request forgery, another potential security risk. Therefore, additional security measures should be implemented to mitigate such threats.

The above is the detailed content of Why Does Google Prefix JSON Responses with `while(1);`?. For more information, please follow other related articles on the PHP Chinese website!