Remove the .NET Framework Assistant 1.0 from Firefox

The newest (3.5 SP1) .NET installs an extension (Microsoft .NET Framework Assistant 1.0) for Firefox (you guessed right: without asking) and even alters the user agent. To maximize “user friendliness”, the uninstall button is inactive. However, regedit helps. Check out “HKEY_LOCAL_MACHINE\SOFTWARE\Mozilla\Firefox\extensions” and delete the key. Other extensions with inactive install buttons, like Google Gears, might be present here as well. That takes care of the unwanted extension, which leaves the user agent. That one can be cleared through deleting “general.useragent.extra.microsoftdotnet”; “microsoft.CLR.clickonce.autolaunch” seems to be of the same origin.
The extensions’ files are located here: \WINDOWS\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\DotNetAssistantExtension\ when everything else is disabled/deleted, you might want to say goodbye to these files too.


Please also browse through the comments, there are some great & helpful additions. Thanks for that! Obviously I wrote this from the perspective of a Windows XP SP3 (x86) user, while more systems (not necessarily in the exact same way) are affected, of course.

//Update 2009/02/09

I just installed Firefox on a machine with .NET 3.5 SP1 already present – Firefox 3.0.6 was immediately “equipped” with the Assistant. There is no escape! :P

//Update 2009/06/01

Oh happy day – the “long and complex”/manual method described above, to remove the .NET Framework Assistant 1.0 from Firefox again, might no longer be necessary. Microsoft itself released a fix (apparently on 2009/May/06) to enable the originally disabled uninstall button again.


In .NET Framework 3.5 SP1, the .NET Framework Assistant enables Firefox to use the ClickOnce technology that is included in the .NET Framework. The .NET Framework Assistant is added at the machine-level to enable its functionality for all users on the machine. As a result, the Uninstall button is shown as unavailable in the Firefox Add-ons list because standard users are not permitted to uninstall machine-level components. In this update for .NET Framework 3.5 SP1 and in Windows 7, the .NET Framework Assistant will be installed on a per-user basis. As a result, the Uninstall button will be functional in the Firefox Add-ons list. This update will also make this version of the .NET Framework Assistant for Firefox compatible with future versions of the Firefox browser. To properly update the .NET Framework Assistant, this update must be applied while the extension is enabled in Firefox. To remedy the result of installing this update while the extension was disabled, uninstall the update, re-enable the extension, and reinstall the update. Updates to the .NET Framework Assistant may include updates to the Windows Presentation Foundation Plug-in for Firefox causing it to be enabled upon its initial update.

//Update 2009/06/02

This is what happened after above patches were installed:

Microsoft .NET Framework Assistant 1.1

About Firefox

The uninstall button is now active as promised and the .NET Framework Assistant version was raised from 1.0 to 1.1. Pressing “Uninstall” successfully clears the user agent too/reverts it to its former state. Happy endings…

  1. OuT

    Hi, here is a little more cleaning…

    delete this reg key:

    delete this file:
    “%SystemRoot%\Microsoft.NET\Framework\v3.5\Windows Presentation Foundation\NPWPF.dll”

    .NET 3 is CRAP. Adds services, adds retarded CardSpace, and now I launch Firefox and I discover Microsoft loaded it with CRAP!! on MY Firefox!! NEVER, NEVER I would let the installer put this shit!! and it even change the user agent!!

    It’s not my habit, but this time I say it: Microsoft you SUCK!!! really.


  2. Mindblowing Maahiya

    Why go thru so much trouble. Don’t install .NET 3.51 in the first place.


  3. Because, unlike the unwanted Firefox Extension, it’s mandatory for many things?
    Also, your ignorance conveniently overlooks that users only learn of this _after_ they install it.
    Anyway, it’s not possible to exclude it from installation… The situation would be another one, if it could be left out by simply clicking an option.


  4. Crowdedhouse


    Where is this please ?


  5. Just type about:config in the address bar and use the filter to find it quickly. Then right-click the entry and choose reset. After a Firefox restart, it’s gone from about:config.

    You can also remove/find it with any editor in the prefs.js in the Firefox profile folder.


  6. Crowdedhouse

    @ nambulous

    Thanks very much !


  7. fantastic

    I couldn’t find the registry key mentioned and was mystified, so if you use Vista 64-bit like me, the registry key to delete this stinker is:



  8. Bozo

    This act of computer sabotage hit me today with an update flagged as “important” – thank’s for the solution of how to get rid of it !


  9. Simon

    If you summarily think that a firefox extension from Microsoft is an “act of computer sabotage”, wait until you discover that your entire operating system also originates from the same company!

    The Linux community welcomes you with open arms – if you don’t trust Microsoft, go to, grab an iso of the latest release in either 32 or 64 bit, and start using that instead of Windows.

    If you were able to find this blog posting, chances are you can use Google to find solutions to any major issues you have after switching (i.e. Hardware related). After that, the system will be able to pass the grandmother test much more smoothly than Windows does.


  10. Mike

    I rarely use windows only when I have to which is pretty rare. I am using fedora 10 and desktop 1.7 snapshot. I prefer BDS over linux. Move over to open source you will love it. No need to worry about virsues and spyware and worrying about a secure update most users wouldn’t know about.


  11. Open up firefox and disable the extension, removing the reg key will make windows update not see it and you will have to reinstall.

    this update is needed for the SP2 which should be released in April so either way we have to install it.

    I myself don’t like items installed secretly so I do understand the issue but come on do you really have to flame over a stupid firefox extension?


  12. Carl

    Kind of funny.
    Microsoft is implicitly accepting that Firefox has enough market penetration to warrant attention. Ergo it implicitly accepts that IE is losing ground. Of course you would never see that publicly stated…


  13. The issue really isn’t the extension itself, it’s the way how it was distributed and how it behaves.

    If Microsoft wants to create Firefox extensions, then _that’s_ fine, but please do normal xpi files like everyone else… Distribute it via and don’t have it disable the uninstall button this is against the standard. I have many extensions installed and I used even more over the years – which are the ones that don’t abide by the rules? Only those from big developers who think they don’t have to.

    The situation would have been _completely okay_, if

    -MS would have used for distribution of a standard xpi
    -.NET 3.5 SP1 wouldn’t have included the Framework Assistant at all or would have made the installation optional
    -the Framework Assistant would show the same behavior people are used to = no disabled uninstall, no modified user-agent…

    These are all very simple things and are taken for granted by heavy users. So there can really be no surprise when people don’t like it.

    Imagine more software would do that, alter the browser in ways the user can’t comprehend before the installation. The user-agent alone could mutate into several lines of BS… This really has to stop before it picks up or it can only end in more and more problems.


  14. me

    Whilst I don’t necessarily approve, I can see the logic.

    Speaking as a professional web developer, it’s a pain that firefox does not support the features that IE6 does- it’s actually a blocker to our users using firefox rather than IE.

    They don’t want to have to choose have a weird addin, they “just want it to work”.

    I want my users to use firefix and for it to “just work”.


  15. Gaspard

    This is the Microsoft MSDN page describing the add-on


  16. Brando

    I just removed the addon using your steps (thanks!) but it did not install “secretly”… at the first FF startup after the .NET update, FF told me that an addon was added…
    Blame to Microsoft for disabling the Uninstall button.


  17. @Brandon

    Nobody said it was secretly. Just that it was installed without asking first. Also, if Firefox wouldn’t tell when an extension was added, lots of people would indeed have learned of it much later, when browsing through the list for other reasons.

    So Mozilla made a good call by developing Firefox this way.


    • James

      Actually Mozilla made a fundamentally bad design decision by allowing anything other than Firefox to install add-ins to the browser.
      If nothing else, from a security point of view it is an attack vector for malicious programs.


  18. finally, thanks for this reference…

    Thank’s very much.


  19. Gary King

    I posted this on Neowin and you were called everything from Paranoid to stupid. Here is the link if you care to read it.


  20. Sexy Namja

    Nice tip for those who dont use .NET and want total control.

    The posts on Neowin were referring to Gary King himself who failed to post the source of the writing later on and chose to stupidly call the add-in “Spyware”

    He then defended himself to the bone calling everyone fanboys and now hes trying to rile a response from the author.

    Gary your paranoid and disillusioned.


  21. Nice tip for those who dont use .NET[…]

    I do use .NET (or some of my programs do) – just not the assistant.

    […]total control.

    No one ever is in…


  22. Ernie

    I have a bunch of saved tabs that require a login so I get a bunch of “Password Required” and “Authentication Required” pop-ups at startup. This MS junk seems to be stealing mouse clicks and making it nearly impossible to get the logins done. While this is going on, it is impossible to cancel the “Add-ons” popup that told me about the new add-on. It even messed up the taskmanager.


  23. Thanks for blogging about this, and especially for posting removal details. I was hit by the damn thing too.


  24. M

    What is ClickOnce, and if I (apparently) haven’t been using it all this time, why would I want/need it?


  25. Dreadneck

    Perhaps Microsoft got the message that firefox users don’t appreciate stealth plugin installs. I found removal instructions for the MS .NET Framework Assistant plugin on Microsoft’s Help & Support site.

    Also, in the ‘More Information’ section on the page, it says that an update is forthcoming that will activate the ‘Uninstall’ button for the plugin. This will be a welcome fix, but MS should learn to ask before installing plugins in Firefox.

    The uninstall instructions can be found here:


  26. jeb

    Running FireFox 3.5 update automatically disables .net framework assistant.


    • Not on any machine I’ve used.

      Besides, what you probably mean, is that Firefox 3.5 (or any higher version) disables all extensions it considers old/incompatible. So that’s the reason.


  27. Gorsefire

    Have just discovered this blog after firefox sent up warnings about net framework asst 1.1. Could someone please enlighten me as top what net framework is and do I need any oft them on my pc?


  28. sonofpearl

    Thanks you so much for this! :-)


  29. so Microsoft installs a plug in , into
    there number one browser competitor,
    doesn’t tell the user, and makes it non removable

    and also , it reduces the browsers security
    BIG surprise

    so i suppose this is not an obvious case of sandbagging?



  30. Why do the Mozilla Org and the Firefox developer prevent such a hacking from Microsoft?

    This is for me a good reason to switch on Linux or to use an alternative browser.


  31. Andrej

    It would be nice if someone creates add-on, which would automatically disable/uninstall all old and new unwanted add-ons and plugins (like ClickOnce, Windows Presentation Foundation and maybe Adobe Acrobat plugin). How about that?


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