diff -r c7c34916027a -r 177826044cd9 wp/wp-includes/class-walker-nav-menu.php
--- a/wp/wp-includes/class-walker-nav-menu.php	Mon Oct 14 18:06:33 2019 +0200
+++ b/wp/wp-includes/class-walker-nav-menu.php	Mon Oct 14 18:28:13 2019 +0200
@@ -34,7 +34,10 @@
 	 *
 	 * @see Walker::$db_fields
 	 */
-	public $db_fields = array( 'parent' => 'menu_item_parent', 'id' => 'db_id' );
+	public $db_fields = array(
+		'parent' => 'menu_item_parent',
+		'id'     => 'db_id',
+	);
 
 	/**
 	 * Starts the list before the elements are added.
@@ -65,7 +68,7 @@
 		 *
 		 * @since 4.8.0
 		 *
-		 * @param array    $classes The CSS classes that are applied to the menu `<ul>` element.
+		 * @param string[] $classes Array of the CSS classes that are applied to the menu `<ul>` element.
 		 * @param stdClass $args    An object of `wp_nav_menu()` arguments.
 		 * @param int      $depth   Depth of menu item. Used for padding.
 		 */
@@ -94,7 +97,7 @@
 			$t = "\t";
 			$n = "\n";
 		}
-		$indent = str_repeat( $t, $depth );
+		$indent  = str_repeat( $t, $depth );
 		$output .= "$indent</ul>{$n}";
 	}
 
@@ -122,7 +125,7 @@
 		}
 		$indent = ( $depth ) ? str_repeat( $t, $depth ) : '';
 
-		$classes = empty( $item->classes ) ? array() : (array) $item->classes;
+		$classes   = empty( $item->classes ) ? array() : (array) $item->classes;
 		$classes[] = 'menu-item-' . $item->ID;
 
 		/**
@@ -137,12 +140,12 @@
 		$args = apply_filters( 'nav_menu_item_args', $args, $item, $depth );
 
 		/**
-		 * Filters the CSS class(es) applied to a menu item's list item element.
+		 * Filters the CSS classes applied to a menu item's list item element.
 		 *
 		 * @since 3.0.0
 		 * @since 4.1.0 The `$depth` parameter was added.
 		 *
-		 * @param array    $classes The CSS classes that are applied to the menu item's `<li>` element.
+		 * @param string[] $classes Array of the CSS classes that are applied to the menu item's `<li>` element.
 		 * @param WP_Post  $item    The current menu item.
 		 * @param stdClass $args    An object of wp_nav_menu() arguments.
 		 * @param int      $depth   Depth of menu item. Used for padding.
@@ -161,16 +164,21 @@
 		 * @param stdClass $args    An object of wp_nav_menu() arguments.
 		 * @param int      $depth   Depth of menu item. Used for padding.
 		 */
-		$id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args, $depth );
+		$id = apply_filters( 'nav_menu_item_id', 'menu-item-' . $item->ID, $item, $args, $depth );
 		$id = $id ? ' id="' . esc_attr( $id ) . '"' : '';
 
-		$output .= $indent . '<li' . $id . $class_names .'>';
+		$output .= $indent . '<li' . $id . $class_names . '>';
 
-		$atts = array();
+		$atts           = array();
 		$atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';
-		$atts['target'] = ! empty( $item->target )     ? $item->target     : '';
-		$atts['rel']    = ! empty( $item->xfn )        ? $item->xfn        : '';
-		$atts['href']   = ! empty( $item->url )        ? $item->url        : '';
+		$atts['target'] = ! empty( $item->target ) ? $item->target : '';
+		if ( '_blank' === $item->target && empty( $item->xfn ) ) {
+			$atts['rel'] = 'noopener noreferrer';
+		} else {
+			$atts['rel'] = $item->xfn;
+		}
+		$atts['href']         = ! empty( $item->url ) ? $item->url : '';
+		$atts['aria-current'] = $item->current ? 'page' : '';
 
 		/**
 		 * Filters the HTML attributes applied to a menu item's anchor element.
@@ -181,10 +189,11 @@
 		 * @param array $atts {
 		 *     The HTML attributes applied to the menu item's `<a>` element, empty strings are ignored.
 		 *
-		 *     @type string $title  Title attribute.
-		 *     @type string $target Target attribute.
-		 *     @type string $rel    The rel attribute.
-		 *     @type string $href   The href attribute.
+		 *     @type string $title        Title attribute.
+		 *     @type string $target       Target attribute.
+		 *     @type string $rel          The rel attribute.
+		 *     @type string $href         The href attribute.
+		 *     @type string $aria_current The aria-current attribute.
 		 * }
 		 * @param WP_Post  $item  The current menu item.
 		 * @param stdClass $args  An object of wp_nav_menu() arguments.
@@ -195,7 +204,7 @@
 		$attributes = '';
 		foreach ( $atts as $attr => $value ) {
 			if ( ! empty( $value ) ) {
-				$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
+				$value       = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
 				$attributes .= ' ' . $attr . '="' . $value . '"';
 			}
 		}
@@ -215,8 +224,8 @@
 		 */
 		$title = apply_filters( 'nav_menu_item_title', $title, $item, $args, $depth );
 
-		$item_output = $args->before;
-		$item_output .= '<a'. $attributes .'>';
+		$item_output  = $args->before;
+		$item_output .= '<a' . $attributes . '>';
 		$item_output .= $args->link_before . $title . $args->link_after;
 		$item_output .= '</a>';
 		$item_output .= $args->after;