Index: src/wp-includes/class-wp-user.php
===================================================================
--- src/wp-includes/class-wp-user.php	(revision 43327)
+++ src/wp-includes/class-wp-user.php	(working copy)
@@ -167,7 +167,7 @@
 	 * @param int    $site_id Optional. The site ID to initialize for.
 	 */
 	public function init( $data, $site_id = '' ) {
-		$this->data = $data;
+		$this->data = apply_filters( 'init_user_data', $data, $site_id );
 		$this->ID   = (int) $data->ID;
 
 		$this->for_site( $site_id );