Ticket #18600: 18600.patch

wp-includes/author-template.php

@@ -385 +385 @@
                 wp_cache_set('is_multi_author', $is_multi_author, 'posts');
         }
 
-        return (bool) $is_multi_author;
+        return apply_filters( 'is_multi_author', (bool) $is_multi_author );
 }
 
 /**