Cross Origin Resource Sharing (CORS) is a way to punch hole in the security brought by a browser. If it is not done carefully, it may result into security vulnerabilities. CORS is an HTTP-header that allows a server to indicate any origins (domain, scheme, or port) other than its own from which a browser should permit loading resources. * can be set by server any allow any origin. This can be abused by an adversary to send cross-origin request from any origin and access the resources for secondary attack.

NOTE: Modern browsers no longer allow * origin with a request that has credentials (cookie header).

Remediation

• Do not allow * origin.
• Specify domains from which requests are allowed.