diff -r 34716fd837a4 -r be944660c56a wp/wp-includes/feed.php
--- a/wp/wp-includes/feed.php	Tue Dec 15 15:52:01 2020 +0100
+++ b/wp/wp-includes/feed.php	Wed Sep 21 18:19:35 2022 +0200
@@ -789,7 +789,6 @@
 		require_once ABSPATH . WPINC . '/class-simplepie.php';
 	}
 
-	require_once ABSPATH . WPINC . '/class-wp-feed-cache.php';
 	require_once ABSPATH . WPINC . '/class-wp-feed-cache-transient.php';
 	require_once ABSPATH . WPINC . '/class-wp-simplepie-file.php';
 	require_once ABSPATH . WPINC . '/class-wp-simplepie-sanitize-kses.php';
@@ -797,11 +796,20 @@
 	$feed = new SimplePie();
 
 	$feed->set_sanitize_class( 'WP_SimplePie_Sanitize_KSES' );
-	// We must manually overwrite $feed->sanitize because SimplePie's
-	// constructor sets it before we have a chance to set the sanitization class.
+	// We must manually overwrite $feed->sanitize because SimplePie's constructor
+	// sets it before we have a chance to set the sanitization class.
 	$feed->sanitize = new WP_SimplePie_Sanitize_KSES();
 
-	$feed->set_cache_class( 'WP_Feed_Cache' );
+	// Register the cache handler using the recommended method for SimplePie 1.3 or later.
+	if ( method_exists( 'SimplePie_Cache', 'register' ) ) {
+		SimplePie_Cache::register( 'wp_transient', 'WP_Feed_Cache_Transient' );
+		$feed->set_cache_location( 'wp_transient' );
+	} else {
+		// Back-compat for SimplePie 1.2.x.
+		require_once ABSPATH . WPINC . '/class-wp-feed-cache.php';
+		$feed->set_cache_class( 'WP_Feed_Cache' );
+	}
+
 	$feed->set_file_class( 'WP_SimplePie_File' );
 
 	$feed->set_feed_url( $url );