Ticket #45283: 45283.diff

src/wp-admin/includes/post.php

@@ -2202 +2202 @@
         wp_nonce_field( 'closedpostboxes', 'closedpostboxesnonce', false );
         // Permalink title nonce.
         wp_nonce_field( 'samplepermalink', 'samplepermalinknonce', false );
+
+        /**
+         * Add hidden input fields to the meta box save form.
+         *
+         * Hook into this action to print `<input type="hidden" ... />` fields, which will be POSTed back to
+         * the server when meta boxes are saved.
+         *
+         * @since 5.0.0
+         *
+         * @params WP_Post $post The post that is being edited.
+         */
+        do_action( 'block_editor_meta_box_hidden_fields', $post );
 }