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Vulnerability In Firefox Popup Blocker

Posted by kdawson on from the all-your-files dept.

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.

6 of 100 comments (clear)

  1. Anyone knows if the 2.x tree is vulnerable too? by A+beautiful+mind · · Score: 5, Informative
    From TFA:

    Vulnerable Systems:
    * Firefox version 1.5.0.9
    Can anyone test?
    --
    It takes a man to suffer ignorance and smile
    Be yourself no matter what they say
    1. Re:Anyone knows if the 2.x tree is vulnerable too? by Tony+Hoyle · · Score: 5, Insightful

      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.

  2. Windows only? by jimbobborg · · Score: 5, Informative

    From the fine article:

    "When the user chooses to manually allow a blocked popup however, normal URL permission checks are bypassed. "

    So you have to MANUALLY disable the popup blocker on a site you don't know in order to make this work. Also, the article keeps talking about c:\whatever. It does not indicate if this is a vulnerability in a non-Windows system.

    1. Re:Windows only? by Tony+Hoyle · · Score: 5, Informative

      From the text it's hardcoded to a specific installation of Windows (not even the default config). It wouldn't work on most systems.

  3. Re:Right... by pairo · · Score: 5, Funny

    That was quite possibly the most ignorant statement I have read on slashdot recently.
    You don't really read much of Slashdot, do you?
  4. Fixed by Anonymous Coward · · Score: 5, Informative

    Already fixed: https://bugzilla.mozilla.org/show_bug.cgi?id=36942 7