/vulndb/Permissive Cross-Origin Resource Sharing

Cross-origin Resource Sharing (CORS) is a specification, which allows Web applications the ability to offer its resources for public consumption from different domains. CORS is typically used in cross-origin APIs designed to be consumed by JavaScript applications.

A vulnerability may arise when the Access-Control-Allow-Origin header permits other pages (hosted on different domains) to access the response body. This may enable some kinds of client-side exploits targeting authenticated users by leveraging vulnerabilities, such as XSS, on 3rd-party applications.

Solution

If CORS is not required than it is advisable to to turn it off. It is important to ensure that the Access-Control-Allow-Origin header is correctly used only on safe resources which will not expose any data from the currently logged in users.

Caveats

Keep in mind that the current finding may be an intended application feature.

References

http://en.wikipedia.org/wiki/Cross-Origin_Resource_Sharing