diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-search-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-search-controller.php
index cc1c302b9c..55fe1ad63a 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-search-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-search-controller.php
@@ -395,7 +395,7 @@ class WP_REST_Search_Controller extends WP_REST_Controller {
 	protected function get_search_handler( $request ) {
 		$type = $request->get_param( self::PROP_TYPE );
 
-		if ( ! $type || ! isset( $this->search_handlers[ $type ] ) ) {
+		if ( ! $type || ! is_string( $type ) || ! isset( $this->search_handlers[ $type ] ) ) {
 			return new WP_Error(
 				'rest_search_invalid_type',
 				__( 'Invalid type parameter.' ),
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 8e0e62e1c4..206923364c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-57836';
+$wp_version = '6.6-alpha-57839';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.