Ticket #15256: 15256.patch

wp-includes/canonical.php

@@ -145 +145 @@
                                 if ( $redirect_url = get_author_posts_url($author->ID, $author->user_nicename) )
                                         $redirect['query'] = remove_query_arg('author', $redirect['query']);
                         }
+                } elseif ( is_category() && !empty($_GET['cat']) && preg_match( '|^[0-9]+$|', $_GET['cat'] ) ) {
+                        if ( $redirect_url = get_term_link( (int) $_GET['cat'], 'category' ) )
+                                $redirect['query'] = remove_query_arg('cat', $redirect['query']);
                 } elseif ( is_category() || is_tag() || is_tax() ) { // Terms (Tags/categories)
 
                         $term_count = 0;