“Imagine you’re a web advertiser. Imagine you can open a popup window from a web page defeating any popup blocker. Imagine this popup can invade the whole desktop, full screen. Imagine this popup has no title bar, no menus, no toolbar, no location bar, no border and no buttons. No mean to close it. Imagine user can’t move or minimize this popup. It will go away only when the browser is killed or your show is done…
Now imagine you’re a phisher. Imagine you can use this almighty popup to draw anything you want. A fake browser or — why not? — a whole fake desktop to collect user’s data.
Impossible wet dreams of clueless evildoers?”
Have a look at Giorgio Maone’s scary article about how Java and Javascript can be abused.