Ticket #40497: 40497.01.patch

src/wp-includes/user.php

@@ -1417 +1417 @@
                         return new WP_Error( 'invalid_user_id', __( 'Invalid user ID.' ) );
                 }
 
+                $userdata['user_login'] = $old_user_data->user_login;
+
                 // hashed in wp_update_user(), plaintext if called directly
                 $user_pass = ! empty( $userdata['user_pass'] ) ? $userdata['user_pass'] : $old_user_data->user_pass;
         } else {
@@ -1442 +1444 @@
         $user_login = trim( $pre_user_login );
 
         // user_login must be between 0 and 60 characters.
-        if ( empty( $user_login ) ) {
+        if ( empty( $user_login ) && ! $update ) {
                 return new WP_Error('empty_user_login', __('Cannot create a user with an empty login name.') );
         } elseif ( mb_strlen( $user_login ) > 60 ) {
                 return new WP_Error( 'user_login_too_long', __( 'Username may not be longer than 60 characters.' ) );