Mike Shaver, Mozilla’s Vice President of Engineering writes:

I’ve previously posted about the .NET Framework Assistant add-on that was delivered via Windows Update earlier this year. It’s recently surfaced that it has a serious security vulnerability, and Microsoft is recommending that all users disable the add-on.

Because of the difficulties some users have had entirely removing the add-on, and because of the severity of the risk it represents if not disabled, we contacted Microsoft today to indicate that we were looking to disable the extension and plugin for all users via our blocklisting mechanism. Microsoft agreed with the plan, and we put the blocklist entry live immediately. (Some users are already seeing it disabled, less than an hour after we added it!)