Ticket #44171: 44171.diff

src/wp-includes/rewrite.php

@@ -273 +273 @@
  */
 function flush_rewrite_rules( $hard = true ) {
         global $wp_rewrite;
+
+        if ( ! is_admin() ) {
+                _doing_it_wrong( __FUNCTION__, __( 'Rewrite rules should only be updated in wp-admin context.' ), '5.0' );
+        }
+
         $wp_rewrite->flush_rules( $hard );
 }