Wordpress can automatically update your installation.
However this can break your site if you have done modifications to the core files of your Wordpress installation, or if any of your installed plug-ins rely on features changed by the update.
In those cases you may want to disable that functionality by adding the following lines to the wp_config.php file:
define('WP_AUTO_UPDATE_CORE', false);
define('AUTOMATIC_UPDATER_DISABLED', true);