Ticket #34299: 34299.diff

src/wp-includes/rest-api/rest-functions.php

@@ -254 +254 @@
                 $url = add_query_arg( 'rest_route', $path, $url );
         }
 
+        if ( is_ssl() ) {
+                // If the current host is the same as REST URL host, force the REST URL scheme to HTTPS
+                if ( $_SERVER['SERVER_NAME'] === parse_url( get_home_url( $blog_id ), PHP_URL_HOST ) ) {
+                        $url = set_url_scheme( $url, 'https' );
+                }
+        }
+
         /**
          * Filter the REST URL.
          *