xDownloadOptions function
This middleware sets the X-Download-Options header to noopen to prevent Internet Explorer users from executing downloads in your site's context.
Some web applications will serve untrusted HTML for download.
By default, some versions of IE will allow you to open those HTML files in the context of your site, which means that an untrusted HTML page could start doing bad things in the context of your pages.
Implementation
Callback xDownloadOptions() {
return (Req req, Res res) {
res.set('X-Download-Options', 'noopen');
};
}