It was found that Internet Explorer allows the disclosure of local file
names. This issue exists due to the fact that Internet Explorer behaves
different for file:// URLs pointing to existing and non-existent files.
When used in combination with HTML5 sandbox iframes it is possible to
use this behavior to find out if a local file exists. This technique
only works on Internet Explorer 10 & 11 since these support the HTML5
sandbox. Also it is not possible to do this from a regular website as
file:// URLs are blocked all together. The attack must be performed
locally (works with Internet zone Mark of the Web) or from a share.