Bug - that's what I get for trying to style a file input. Try clicking just to the left or right of it.
The other thing that is rather confusing is that having selected the file, it's not clear how to proceed. I eventually clicked 'What have I missed' which seems to actually be 'I've not missed anything please click this button' - I think this could be better worded to just 'Go' or something similar once the file is selected.