Cross-Origin Resource Sharing (CORS) is a security mechanism that allows servers to specify which origins can access their resources, relaxing the Same-Origin Policy (SOP) for legitimate cross-origin requests. CORS uses specific HTTP headers to control this access. The key header for controlling access to resources isAccess-Control-Allow-Origin, which specifies which origins are permitted to access the resource. However, among the provided options, the closest related header isAccess-Control-Allow-Headers, which is part of the CORS standard and controls which request headers can be used in the actual request (e.g., during a preflight OPTIONS request).
Option A ("Access-Control-Request-Method"): This header is sent by the client in a preflight request to indicate the HTTP method (e.g., GET, POST) that will be used in the actual request. It is not used by the server to control access.
Option B ("Access-Control-Request-Headers"): This header is sent by the client in apreflight request to list the headers it plans to use in the actual request. It is not used by the server to control access.
Option C ("Access-Control-Allow-Headers"): This header is sent by the server in response to a preflight request, specifying which headers are allowed in the actual request. While Access-Control-Allow-Origin is the primary header for controlling access, Access-Control-Allow-Headers is part of the CORS standard to manage header-based access control, making this the best match among the options.
Option D ("None of the above"): Incorrect, as Access-Control-Allow-Headers is a CORS header.
The correct answer is C, aligning with the CAP syllabus under "CORS Security" and "HTTP Headers."References: SecOps Group CAP Documents - "CORS Configuration," "Security Headers," and "OWASP Secure Headers Guide" sections.
