As of SAP NW Release 7.51, the HTTP Whitelist functionality has been integrated into the Unified Connectivity (UCON) concept. This new UCON based whitelist provides an additional logging / simulation phase, and also the additional functionality Cross-origin Resource Sharing (CORS). However in release 7.51, also the old whitelist check (based on the HTTP_WHITELIST table) is supported.
For details, refer to the below Help articles:
Managing HTTP Whitelists
HTTP Whitelist Scenario: Process
Note: It is possible to activate the UCON based whitelist check, even if no white list entries are maintained. As a result, all HTTP calls will be rejected with HTTP 500 errors. See the KBA 2704178 for details.