Mozilla blocks Microsoft's buggy Firefox plugin

Microsoft silently installed the .Net plugin earlier this year

Mozilla developers have blocked a Firefox plugin that was quietly pushed out by Microsoft, saying that it presents a security risk.

Microsoft shipped the Firefox add-on as part of a .Net software update last February, causing outrage among some Firefox users, who complained that the software was sneaked onto their systems without their knowledge or approval and was extremely difficult to remove.

On Tuesday, Microsoft warned that Firefox users who have not applied a recent Internet Explorer patch were vulnerable to a "browse-and-get-owned attack" because of a bug in the Microsoft .Net Framework Assistant add-on.

"All that is needed is for a user to be lured to a malicious website," Microsoft said. Triggering this vulnerability involves the use of a malicious XBAP (XAML Browser Application).

The flaw is a nasty one, but users who have installed the MS09-054 IE update, released Tuesday are protected from this attack, "regardless of the attack vector," Microsoft said.

To protect users who may not have installed Microsoft's patch, Mozilla is automatically blocking two add-ons: the Microsoft .Net Framework Assistant and a related plugin called the Windows Presentation Foundation. The open-source browser started blocking the software late Friday night.

"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," wrote Mozilla Vice President of Engineering Mike Shaver in a blog posting. "Microsoft agreed with the plan, and we put the blocklist entry live immediately."

Buggy plugins are a growing problem, as cyber criminals have increasingly leveraged flaws in products such as Adobe Flash Player and QuickTime to launch browser-based attacks. Earlier this week, Mozilla launched a Plugin Check site where Firefox users can see if their plugins are up-to-date.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags MicrosoftFirefoxmozillaexploits and vulnerabilities

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Robert McMillan

IDG News Service
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Tom Pope

Dynabook Portégé X30L-G

Ultimately this laptop has achieved everything I would hope for in a laptop for work, while fitting that into a form factor and weight that is remarkable.

Tom Sellers

MSI P65

This smart laptop was enjoyable to use and great to work on – creating content was super simple.

Lolita Wang

MSI GT76

It really doesn’t get more “gaming laptop” than this.

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Featured Content

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?