Ha! The Windows Store is a scum-ridden wasteland. The second top result for Facebook is a fake scam app, claiming to be official. There is a fake Facebook app, paid, that claims to be published by "@Microsoft Corporation". Contacting Store support results in them telling you the app " works as designed ", and if you have a problem with the fake publisher, MS suggests " leave a review ".
Even Netflix had a hard time preventing fakes from being published. Over a month or two, Netflix had to contact MS several times, and MS didn't suspend or remove the publisher. They resubmitted and got listed again. Try searching for HBO, xfinity, etc.
MS is not interested in fixing this problem. Probably some folks have their bonus tied to " number of apps published " and that's that.
I emailed Satya and the manager of the Store, to book effect. The Store is a joke.
For this particular case, if FileZilla is popular, you'll have several fake paid apps. If you're lucky there may be av official app, with no way to verify it's the right one. For most users, they'll be rolling the dice just as much as they are now. Only if FileZilla is extremely diligent would it work. Disney, for example, is a top publisher for the Store, yet all sorts of fake Disney content is on there. I called Disney about this, and after about 15 minutes they figured out "don't go there" (referring to the Store). Even top publishers have a hard time dealing with it. BBC is another case, where top "official" results aren't.