Vulnerability In Firefox Popup Blocker

cj writes in with news of a vulnerability in Firefox's stock popup blocker discovered by Michal Zalewski. The vulnerability can allow a malicious user to read files from an affected system. The attacker would "need to plant a predictably named file with exploit code on the target system. This sounds hard, but isn't," according to the article.

Comments

Re:Anyone knows if the 2.x tree is vulnerable too?

[Tony Hoyle]

Can anyone test?

Nope, because no example exploit is given and the means of exploitation looks rather unlikely:

"To create a popup warning, a script embedded on the page calls: window.open('file:///c:/windows/temp/xxxxxxx.htm', 'new2',''),

with a name calculated by repeating a procedure implemented in SetUpTempFile() with a seed calculated by the server based on reported system time (p2.html?time)."

1. It assumes that the temp file is c:/windows/temp. It isn't, unless you're running Windows 95, and only then if you've not changed it from default. That's the *system* default temp file. The *user* temp directory is inside local settings in the user specific area (much harder to find out remotely. Maybe not impossible, but you'd have to get lucky (it's not just the username as the directory name.. it has things like .000 after it).
2. Calculating the seed to that accuracy is damned hard.