http://www.robertnyman.com/2009/01/26/microsoft-force-installs-firefox-extension/ –

Microsoft seems to think silently installing extensions for 3rd party software (READ: Mozilla Firefox web browser) through their native “Windows Update” service would be a good thing.

The following people, however, beg to differ:

http://www.robertnyman.com/2009/01/26/microsoft-force-installs-firefox-extension/
http://nambulous.wordpress.com/2008/08/23/remove-the-net-framework-assistant-10-from-firefox
http://wyday.com/blog/2008/how-to-uninstall-microsoft-net-framework-assistant-from-firefox
http://support.mozilla.com/tiki-view_forum_thread.php?locale=en-US&comments_parentId=265132&forumId=1