The Wiper Technologies catalog is pretty darn accurate in their application chart ...or so we've found through the years on this and other RV forums.
RVupgrades has been selling Wiper Technologies wiper blades for years (they are a forum vendor and the owner is the founder of iRV2). Wiper Technologies wiper blades are heavy-duty, are well made, and will last a lot longer than the cheaper ones you might buy for your car. Yes, they cost a lot more but not only last longer but perform better too --or at least in my experience using them.
So your application for a 2008 Fiesta would be a WT6-26
Wiper Technologies WT6-26 Heavy Duty Wiper Blade - 26"
RVupgrades.com is one of the better, if not the best, online vendors I've used for RV accessories and some parts. They have very good customer service and fast shipping. I'm pretty sure they'd work with you if what you order doesn't fit, etc. and you have to return or exchange them.
Here's a screen shot of the Wiper Technologies catalog page for your application or you can go HERE
for the complete catalog.