Wt

This can be seen in the widget gallery: https://www.webtoolkit.eu/widgets/forms/file-upload

If you go to the file upload directly with a JavaScript-enabled browser, then (because of progressive bootstrap) it will first load an <input type="file"> based WFileUpload, but then quickly replace it with the iframe-based one. This is fine, but the theme applies some styling to this input that sticks around.