Microsoft Is Screwing With My Firefox

I like to keep my installation of Firefox free from Microsoft products, but it seems that Microsoft doesn't like that. Today I had Microsoft Update pop up and say I needed to install the Microsoft .NET Framework 3.5 Service Pack 1 and .NET Framework 3.5 Family Update. It had the update listed as important so I went ahead and installed it. Unfortunately, it changed my user agent, installed an extension and a plugin in Firefox without asking or telling me. Apparently these additions are yet another proprietary Microsoft technology, this time to allow web browsers to run .NET programs as if they were installed locally on the computer. I haven't looked into it much, but that seems like a big security risk to me and if I absolutely need to use it (which I doubt), I can always run Internet Explorer.



To remove the Microsoft .NET Framework Assistant extension, I did some searching on the Internet and found these instructions from

  • Open regedit
  • Go to "HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\Firefox\extensions" for 32bit versions of Windows
    or "HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Mozilla\Firefox\extensions" for 64-bit versions of Windows
  • Right click on the key "{20a82645-c095-46ed-80e3-08825760534b}" and click Delete
  • Go to "HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins"
    or "HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins" for 64bit versions of Windows
  • Right click on the key ",version=3.5" and click Delete



To remove the Windows Presentation Foundation plugin, I found the following from the mozillaZine forums:

  • Open Windows Explorer
  • Go to "C:\Windows\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation"
  • Right click on the "NPWPF.dll" file and click Delete
  • Restart Firefox if you have it open


To remove the Microsoft .NET user agent string, do the following:

  • Open a new window or tab in Firefox and type "about:config" in the address bar
  • Click on the I'll be careful, I promise! button
  • Type "microsoft" in the filter bar
  • Right click on the entry "general.useragent.extra.microsoftdotnet" and choose the Reset option


Once you restart Firefox, it will all be removed.


Bonus Errors

As an added bonus, I started seeing a message that said "This site may harm your computer" on every search result from Google. I mistakenly thought this was caused by the new .NET Firefox addons as this problem started after Windows Update rebooted my computer and went away after I removed the addons. As it turns out, it was just a human error that Google quickly fixed and has promised to put checks in place to keep it from happening again.