plupload uses something like this input type="file"
<input id="html5_197263a5ok7gmcou4a2q512e05" type="file" style="font-size: 999px; opacity: 0; position: absolute; top: 0px; left: 0px; width: 100%; height: 100%;" multiple accept>
inside a DIV with class="moxie-shim moxie-shim-html5" and 0 dimensions:
style="position: absolute; top: 0px; left: 0px; width: 0px; height: 0px; overflow: hidden; z-index: 0;"
Navigate this page with the Tab key on your keyboard: all tested browsers focus all the fields except Safari which skips the invisible (or semi-invisible) ones (Firefox doesn't show the focus styles, but it does focus all the fields).