Harden index.html warning dismissal handler (#1034)

* Harden index.html warning dismissal handler

* Fix indentation

* Linting fix, single quotes only here

Author: donnchawp

wp-cache.php

@@ -2096,9 +2096,14 @@ function wpsc_config_file_notices() {
 }
 add_action( 'admin_notices', 'wpsc_config_file_notices' );
 function wpsc_dismiss_indexhtml_warning() {
-		check_ajax_referer( "wpsc-index-dismiss" );
-		update_site_option( 'wp_super_cache_index_detected', 3 );
-		die( 0 );
+	check_ajax_referer( 'wpsc-index-dismiss' );
+
+	if ( ! current_user_can( 'manage_options' ) ) {
+		wp_send_json_error( null, 403 );
+	}
+
+	update_site_option( 'wp_super_cache_index_detected', 3 );
+	die( 0 );
 }
 add_action( 'wp_ajax_wpsc-index-dismiss', 'wpsc_dismiss_indexhtml_warning' );