diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/bookmark-template.php
--- a/wp/wp-includes/bookmark-template.php	Tue Jun 09 11:14:17 2015 +0000
+++ b/wp/wp-includes/bookmark-template.php	Mon Oct 14 17:39:30 2019 +0200
@@ -195,7 +195,7 @@
  *                                      $categorize is true. Accepts 'ASC' (ascending) or 'DESC' (descending).
  *                                      Default 'ASC'.
  * }
- * @return string|null Will only return if echo option is set to not echo. Default is not return anything.
+ * @return string|void Will only return if echo option is set to not echo. Default is not return anything.
  */
 function wp_list_bookmarks( $args = '' ) {
 	$defaults = array(
@@ -214,6 +214,12 @@
 
 	$output = '';
 
+	if ( ! is_array( $r['class'] ) ) {
+		$r['class'] = explode( ' ', $r['class'] );
+	}
+ 	$r['class'] = array_map( 'sanitize_html_class', $r['class'] );
+ 	$r['class'] = trim( join( ' ', $r['class'] ) );
+
 	if ( $r['categorize'] ) {
 		$cats = get_terms( 'link_category', array(
 			'name__like' => $r['category_name'],
@@ -242,7 +248,7 @@
 				$r['category_before']
 			);
 			/**
-			 * Filter the bookmarks category name.
+			 * Filters the bookmarks category name.
 			 *
 			 * @since 2.2.0
 			 *
@@ -283,7 +289,7 @@
 	}
 
 	/**
-	 * Filter the bookmarks list before it is echoed or returned.
+	 * Filters the bookmarks list before it is echoed or returned.
 	 *
 	 * @since 2.5.0
 	 *