Looks like Rally Armor has a link for a product for the Fiesta ST on their website. However, it's listed as in development and to be released shortly. Hopefully soon!
http://www.rallyarmor.com/index.php/rally-mud-flaps-2014-ford-fiesta
http://www.rallyarmor.com/index.php/rally-mud-flaps-2014-ford-fiesta