- Log into your site, put it into maintenance mode ~/admin/config/development/maintenance and back up all files.
- Log into cPanel and start the cPanel file manager.
- Go to the root directory, usually /public_html.
- Delete all Folder & files except Modules, Profile, Sites, Themes
- Upload latest drupal version - example: Drupal-8.4.8.tar.gz and extract it.
- Copy all files and folders EXCEPT: Modules, Profile, Sites, Themes folder to the root directory.
- Log into your site and run database updates ~/update.php
- Check the Status report ~/admin/reports/status.
- If all OK take the site out of maintenance mode