Mozilla announced on Friday through its official blog the blockade of Microsoft plug-in for Firefox called the .Net Framework Assistant based on security concerns. According to the post, the add-on have a high risk of causing stability or security problem.

Mozilla's VP of engineering, Mike Shaver, announced the preliminary step in the post that: '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 plug-in for all users via our blocklisting mechanism'.

It is also confirmed that Microsoft had agreed with the plan, and that blocklist entry went live immediately. Microsoft is recommending that all users disable the add-on.

Though the blockade was intended to protect users, but on-the-other hand it had generated other issues: removing it initially required people to edit their Windows Registry - a technically tussle many would not undertake. It was automatically installed via Windows Update with the .Net Framework 3.5 Service Pack 1 without telling the user that the add-on was being installed neither given any options. More hackles were raised because it wasn't compatible with Firefox 3.5.