It appears that Microsoft is quietly slipping in a Firefox extension with updates to the .NET framework. The extension is named "Microsoft .NET Framework Assistant" and, based on the description, "Adds ClickOnce support and the ability to report installed .NET versions to the web server." According to reports, this extension:

• Cannot be uninstalled through Firefox
• Changes the Firefox user-agent string
• Does God knows what else

Happily, people have figured out how to uninstall the extension. This move seems pretty dirty to me, but Microsoft has been pointed in this direction for some time now. If you find yourself 'infected' with this piece of malware, do yourself a favor and remove it.