Index: src/wp-includes/user.php
===================================================================
--- src/wp-includes/user.php	(revision 42525)
+++ src/wp-includes/user.php	(working copy)
@@ -1803,6 +1803,8 @@
 		$user->set_role( $userdata['role'] );
 	} elseif ( ! $update ) {
 		$user->set_role( get_option( 'default_role' ) );
+	} elseif( ( isset( $_GET['action'] ) ) && ( $_GET['action'] == "register" ) ) {
+		$user->set_role( '' );
 	}
 	wp_cache_delete( $user_id, 'users' );
 	wp_cache_delete( $user_login, 'userlogins' );
Index: src/wp-login.php
===================================================================
--- src/wp-login.php	(revision 42525)
+++ src/wp-login.php	(working copy)
@@ -653,7 +653,11 @@
 
 		if ( isset( $_COOKIE[ $rp_cookie ] ) && 0 < strpos( $_COOKIE[ $rp_cookie ], ':' ) ) {
 			list( $rp_login, $rp_key ) = explode( ':', wp_unslash( $_COOKIE[ $rp_cookie ] ), 2 );
-			$user                      = check_password_reset_key( $rp_key, $rp_login );
+			$user = check_password_reset_key( $rp_key, $rp_login );
+			// Get user form using WP_User query with user ID argument.
+			$update_user = new WP_User( $user->ID );
+			// Update default role for register user from admin side.
+			$update_user->set_role( get_option( 'default_role' ) );
 			if ( isset( $_POST['pass1'] ) && ! hash_equals( $rp_key, $_POST['rp_key'] ) ) {
 				$user = false;
 			}