Ticket #40760: 40760.diff

src/wp-includes/class-walker-page.php

@@ -61 +61 @@
                         $n = '';
                 }
                 $indent = str_repeat( $t, $depth );
-                $output .= "{$n}{$indent}<ul class='children'>{$n}";
+
+                // Default CSS class.
+                $classes = array( 'children' );
+
+                /**
+                 * Filters the CSS class(es) applied to a page children list element.
+                 *
+                 * @since 4.8.0
+                 *
+                 * @param array $classes The CSS classes that are applied to the menu `<ul>` element.
+                 * @param array $args    Arguments for outputting the next level.
+                 * @param int   $depth   Depth of page. Used for padding.
+                 */
+                $class_names = join( ' ', apply_filters( 'page_children_list_css_class', $classes, $args, $depth ) );
+                $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
+
+                $output .= "{$n}{$indent}<ul {$class_names}>{$n}";
         }
 
         /**