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Firefox blocks and backtracks on 'insecure' MS add-ons

Plug-in peril confusion

Mozilla disabled two Microsoft developed Firefox add-ons over the weekend after deciding the applications posed a security risk. It has since revised its safety assessment and set about removing the plugins from its blacklist.

The Microsoft Framework 1.1 Assistant FireFox extension and Microsoft Windows Presentation Foundation Firefox plugin were both branded as unstable and consigned to application limbo on Friday. Firefox fans who had the plug-ins installed received a pop-up notice explaining that "unstable or insecure add-ons" have been disabled, the Washington Post reports.

A patch for Microsoft .NET published in May installed both the Microsoft .NET Framework Assistant and Windows Presentation Foundation plug-ins onto Firefox. This installation happened without the informed consent of Mozilla users and, worse still, was difficult to undo without editing the Windows Registry.

Redmond responded to the issue by publishing a simple tool to remove Microsoft .NET Framework Assistant. Last week concerns emerged the component could be used to launch security attacks against Firefox users.

The potential issue emerged shortly after Microsoft published a cumulative security update for Internet Explorer as part of a bumper patch batch last week. Acting over concerns that Firefox users who were late in applying this patch might be exposed to attack, Mozilla applied changes to neuter both the Windows Presentation and Microsoft Framework 1.1 Assistant plugins.

Mike Shaver, Mozilla's vice president of engineering, explained Mozilla's intervention in a blog posting last Friday.

"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."

However, it subsequently emerged that the Microsoft Framework Assistant add-on poses no threat to Firefox users. Mozilla is in the process of removing both components from its blocklist, as explained in Shaver's latest post here. ®

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