diff -r 48c4eec2b7e6 -r 8c2e4d02f4ef wp/wp-includes/class-wp-simplepie-sanitize-kses.php
--- a/wp/wp-includes/class-wp-simplepie-sanitize-kses.php	Fri Sep 05 18:40:08 2025 +0200
+++ b/wp/wp-includes/class-wp-simplepie-sanitize-kses.php	Fri Sep 05 18:52:52 2025 +0200
@@ -7,16 +7,21 @@
  * @since 4.7.0
  */
 
+// Don't load directly.
+if ( ! defined( 'ABSPATH' ) ) {
+	die( '-1' );
+}
+
 /**
  * Core class used to implement SimplePie feed sanitization.
  *
- * Extends the SimplePie_Sanitize class to use KSES, because
+ * Extends the SimplePie\Sanitize class to use KSES, because
  * we cannot universally count on DOMDocument being available.
  *
  * @since 3.5.0
  */
 #[AllowDynamicProperties]
-class WP_SimplePie_Sanitize_KSES extends SimplePie_Sanitize {
+class WP_SimplePie_Sanitize_KSES extends SimplePie\Sanitize {
 
 	/**
 	 * WordPress SimplePie sanitization using KSES.
@@ -33,17 +38,17 @@
 	 */
 	public function sanitize( $data, $type, $base = '' ) {
 		$data = trim( $data );
-		if ( $type & SIMPLEPIE_CONSTRUCT_MAYBE_HTML ) {
+		if ( $type & SimplePie\SimplePie::CONSTRUCT_MAYBE_HTML ) {
 			if ( preg_match( '/(&(#(x[0-9a-fA-F]+|[0-9]+)|[a-zA-Z0-9]+)|<\/[A-Za-z][^\x09\x0A\x0B\x0C\x0D\x20\x2F\x3E]*' . SIMPLEPIE_PCRE_HTML_ATTRIBUTE . '>)/', $data ) ) {
-				$type |= SIMPLEPIE_CONSTRUCT_HTML;
+				$type |= SimplePie\SimplePie::CONSTRUCT_HTML;
 			} else {
-				$type |= SIMPLEPIE_CONSTRUCT_TEXT;
+				$type |= SimplePie\SimplePie::CONSTRUCT_TEXT;
 			}
 		}
-		if ( $type & SIMPLEPIE_CONSTRUCT_BASE64 ) {
+		if ( $type & SimplePie\SimplePie::CONSTRUCT_BASE64 ) {
 			$data = base64_decode( $data );
 		}
-		if ( $type & ( SIMPLEPIE_CONSTRUCT_HTML | SIMPLEPIE_CONSTRUCT_XHTML ) ) {
+		if ( $type & ( SimplePie\SimplePie::CONSTRUCT_HTML | \SimplePie\SimplePie::CONSTRUCT_XHTML ) ) {
 			$data = wp_kses_post( $data );
 			if ( 'UTF-8' !== $this->output_encoding ) {
 				$data = $this->registry->call( 'Misc', 'change_encoding', array( $data, 'UTF-8', $this->output_encoding ) );