PHP message: PHP Fatal error: Uncaught Error: Undefined constant "ABS…

…PATH direct access to wp-includes/rss.php on line 19

https://core.trac.wordpress.org/ticket/61277

src/wp-includes/rss.php

@@ -12,7 +12,9 @@
  * @subpackage MagpieRSS
  * @deprecated 3.0.0 Use SimplePie instead.
  */
-
+if ( ! defined( 'ABSPATH' ) ) {
+    exit; // Exit if accessed directly
+}
 /**
  * Deprecated. Use SimplePie (class-simplepie.php) instead.
  */