[Full-disclosure] Firefox: about:blank is phisher's best friend

[Michael Wojcik]

> From: Michal Zalewski [mailto:lcamtuf at dione.ids.pl] 
> Sent: Friday, 16 February, 2007 17:51
> To: bugtraq at securityfocus.com
> Cc: full-disclosure at lists.grok.org.uk
> 
> Firefox suffers from a design flaw that can be used to confuse casual
> users and evoke a false sense of authority when visiting a fraudulent
> website. ...
> 
> It is possible for a script to open 'about:blank' URL in a new tab;
this
> tab will be opened with a blank address bar (the behavior is different
for
> new windows, where the bar will be grayed out or hidden).

Nice work, as always.  A couple of points:

- Disabling Javascript for the attacking site prevents these attacks
from working, of course.  Firefox's NoScript extension, which implements
a scripting whitelist in a highly usable fashion, works nicely for this
sort of thing.  It will also prevent scripts from about:blank by
default, though that's of limited use here.

Unfortunately, it's unlikely that "casual users" will have NoScript
installed, though I'm happy to see that it's one of the most popular
Firefox extensions.

- The third attack on your page ("Test it through about:blank proxy"),
which is designed to open a spoofed-UI window with a "normal" title bar,
produced a window with the title "about: - Google - Mozilla Firefox" on
my test system (once I had NoScript temporarily allow Javascript from
your site).  I don't know offhand why I got the "about: -" prefix;
perhaps because NoScript disables Javascript from "about:blank" by
default?

-- 
Michael Wojcik
Principal Software Systems Developer, Micro Focus