Cross-origin resource sharing (CORS) is a browser mechanism which enables controlled access to resources located outside of a given domain.
Misconfigured CORS
Step->1. Capture the target website and spider or crawl all the website using burp.
Step->2. Use burp search look for Access-Control
Step->3. Try to add Origin Header i.e,Origin:attacker.com or Origin:null or Origin:attacker.target.com or Origin:target.attacker.com
Step->4 If origin is reflected in response means the target is vuln to CORS