Testing CORS
An application implementing HTML5 Cross-Origin Resource Sharing (CORS) means the application will share browser information with another domain that resides at a different origin. By design, browser protections prevent external scripts from accessing information in the browser. This protection is known as Same-Origin Policy (SOP). However, CORS is a means of bypassing SOP permissively. If an application wants to share browser information with a completely different domain, it may do so with properly configured CORS headers.
Web-penetration testers must ensure applications that handle AJAX calls (for example, HTML5) do not have misconfigured CORS headers. Let’s see how Burp Suite can help us identify such misconfigurations.
Getting ready
Log in to your PortSwigger account. Using Lab: CORS vulnerability with basic origin reflection (https://portswigger.net/web-security/cors/lab-basic-origin-reflection-attack), we will see how to identify a CORS vulnerability...
