Internet Explorer Can Affect Firefox

Martin Brinkmann
Apr 22, 2010
Updated • Apr 13, 2018

One would think that web browsers run independently of each other, that Google Chrome and Firefox, or Firefox and Internet Explorer would not affect each other.

Michael Horowitz over on Computerworld just found out that Internet Explorer can affect Firefox on Windows XP.

He changed the security level of Internet Explorer to high recently to improve the security level of the browser and harden it, and noticed from then on that Firefox would not download executable files anymore.

He linked it first to the recent service pack download and installation for Windows XP but found out later that it was actually a consequence of setting Internet Explorer's Internet Zone setting to high.

Firefox would not save executable files with the *.exe extension to folders on the operating system. The files would be created normally but with 0 Kilobyte. Firefox itself would cancel the downloads in the download manager right after they had been added to it.

firefox internet explorer

Michael then tried to download executables with Chrome which worked out fine. He then knew that the issue was related to Firefox and discovered ways to resolve the issue directly in Firefox, at least for pre- and post Firefox 3.6 versions.

In Firefox 3.5 and 3.7 you need to enter "about:config" (no quotes) in the address bar and click through the warning about voiding the warranty.

  • In Firefox 3.5.x the new option is called and it should be set to True.
  • In Firefox 3.7.x and newer, the new option is called and it should be set to False.

Starting with Firefox 3, the Windows security settings for downloading applications and other potentially unsafe files from the Internet are honored on files downloaded by the Download Manager.

This allows, for instance, system administrators to block executable files from being downloaded by Firefox. This preference allows Firefox to ignore those OS-wide security checks.

Starting with Firefox 3.6, this preference is no longer used. (source)

In Firefox 3, if a Windows user has an antivirus program installed, it is launched to scan files when they finish downloading. During testing of the feature, concerns about delays and double-scanning files surfaced. As a result, this preference—controlling whether the virus scan is automatically triggered—was created.

Starting in Firefox 3.7 (3.7a3pre nightly builds since 2010-03-06) this preference also controls whether or not the Windows security policy checks are applied for downloading and launching executable files. (source)

The new policy means that it is possible to resolve the issue in all versions of Firefox except the 3.6x branch. Firefox 3.6 users running Windows XP are affected by this if the Internet Zone of Internet Explorer is set to high.

Their options are to download executable files with another web browser, switch to a different version of Firefox or customize the settings in Internet Explorer so that executable files can be downloaded.

Internet Explorer Can Affect Firefox
Article Name
Internet Explorer Can Affect Firefox
Internet Explorer settings may affect the Firefox web browser under certain circumstances. Find out how to configure Firefox either way.
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  1. Blubba said on April 26, 2010 at 12:39 am

    Sheesh, ist this “Martin” 14 or 15 yo?
    Nice tips for something that is known since FF3.0.
    In FF3.0 it was introduced as a feature, and now this moron treats it as a bug?

    Get a grip dude.

  2. Navesh said on April 22, 2010 at 8:44 pm

    What planet are you people living on, Firefox runs on the IE security settings on XP this has been known for ages?

  3. GiddyUpGo said on April 22, 2010 at 8:22 pm

    Another way around this after you set IE to high is to select the custom tab and then select
    “Prompt (Recommended)”
    for “Launching Applications and Unsafe Files”
    I knew about this a long time ago but only now knew about the About-Config setting.

  4. ramooonas said on April 22, 2010 at 8:14 pm

    I run latest FF3.6.3 on Višta, and also had the same problem to
    download .exe files. I set “
    scanWhenDone” to False and vualia, it works. Thanks.

    1. Michael Horowitz said on April 22, 2010 at 9:01 pm

      Strange. I tested this on XP, Vista and Windows 7 and only had a
      problem saving files on XP. Vista worked fine for me.

  5. Jim said on April 22, 2010 at 2:12 pm

    When I try to enter “about.config” FireFox puts in the http:// for me and sends me to a website. How do I get around this??

    1. Martin said on April 22, 2010 at 3:42 pm

      You need to enter about:config

      1. Kay said on April 23, 2010 at 4:57 am

        when you type ‘about config’, you are missing one thing that is critical: what you are typing is aboutconfig. in actuality, you need to type aboutconfig. It will then look like this: about:config.

      2. Jim said on April 22, 2010 at 4:14 pm

        Martin, that is exactly what I do. I type about.config in the address bar (no quotes) and FireFox 3.6.3 sends me to a search website (my ISPs default “I can’t find the website you asked for search site) because FireFox is automatically adding the http:// in front of the text I typed. It ends up looking for http://about.config instead of just about.config.

      3. Martin said on April 22, 2010 at 4:28 pm

        You again state that you enter about.config and not about:config

      4. Jim said on April 22, 2010 at 4:39 pm

        Finally! Must be my 48 year old eyes and not using my glasses…. I hate it when I am publicly foolish and fail to distinguish “:” from “.”. Sigh…thank you for your patience!

      5. Martin said on April 22, 2010 at 4:44 pm

        Glad that it sorted itself out ;)

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