diff --git a/wp-admin/includes/class-wp-upgrader.php b/wp-admin/includes/class-wp-upgrader.php
index 1fbfa99e4c..c54384e742 100644
--- a/wp-admin/includes/class-wp-upgrader.php
+++ b/wp-admin/includes/class-wp-upgrader.php
@@ -196,6 +196,7 @@ class WP_Upgrader {
 		/* translators: %s: Directory name. */
 		$this->strings['fs_no_folder'] = __( 'Unable to locate needed folder (%s).' );
 
+		$this->strings['no_package']           = __( 'Package not available.' );
 		$this->strings['download_failed']      = __( 'Download failed.' );
 		$this->strings['installing_package']   = __( 'Installing the latest version…' );
 		$this->strings['no_files']             = __( 'The package contains no files.' );
@@ -527,7 +528,10 @@ class WP_Upgrader {
 			set_time_limit( 300 );
 		}
 
-		if ( empty( $source ) || empty( $destination ) ) {
+		if (
+			( ! is_string( $source ) || '' === $source || trim( $source ) !== $source ) ||
+			( ! is_string( $destination ) || '' === $destination || trim( $destination ) !== $destination )
+		) {
 			return new WP_Error( 'bad_request', $this->strings['bad_request'] );
 		}
 		$this->skin->feedback( 'installing_package' );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 5a64e4d883..f034d44edd 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-58021';
+$wp_version = '6.6-alpha-58022';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.