After the upgrade in EZP-26870 the upload button overlay does not fully cover the underlying html buttons, on firefox and chrome at least. See screenshot, and saved page in zip.

Note: also take notice that when uploading files, the process itself however fast, will span the Cancel button that will also show partially overlapped to the right of the upload button. This seemed to happen only on Firefox though, since on Chrome the overlapping button is much wider and showed covering the space for both buttons.