Firefox Moves To Block Java, Silverlight, Adobe Reader

Mozilla's "click to play" move will block all plug-ins from executing without explicit user authorization.

Mozilla has announced that all Firefox plug-ins, barring the most recent version of Flash, will soon require explicit user authorization before being allowed to run.

"Mozilla is changing the way Firefox loads third party plug-ins such as Flash, Java and Silverlight," said Michael Coates, director of security assurance for Mozilla, in a blog post. "This change will help increase Firefox performance and stability and provide significant security benefits, while at the same time providing more control over plug-ins to our users."

Mozilla's move come in the wake of widespread, in-the-wild attacks against the Java browser plug-in, related user security confusion and warnings that new zero-day vulnerabilities in Java -- not yet exploited by attackers -- have been disclosed to Oracle and not yet patched.

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"Leveraging Click to Play, Firefox will only load plug-ins when a user takes the action of clicking to make a particular plug-in play, or the user has previously configured Click To Play to always run plug-ins on the particular website," said Coates.

With click to play, Firefox was set to automatically block plug-ins that Mozilla deemed to pose a significant security or stability risk. "This includes vulnerable and outdated versions of Silverlight, Adobe Reader and Java," said Coates. But the security blocks had stopped there. "Previously Firefox would automatically load any plug-in requested by a website," he said.

Click-to-play capabilities have long been lauded by security experts for adding an extra level of protection that helps block the silent exploitation of vulnerable plug-ins. Of course, like so many types of security, there's a caveat: users will have to pay attention to warnings, and not allow plug-ins to run that shouldn't be running.

Adobe, which develops Flash Player and Adobe Reader -- and which has already enjoyed the attentions now being paid to Java by attackers -- has lauded Mozilla's move to block all browser plug-ins from automatically running. "The Adobe team has worked hard to improve patch adoption by delivering background updaters for Flash Player and Adobe Reader. In addition, we have worked with partners, such as Microsoft and Google, to reduce update fatigue by delivering patches through existing update mechanisms," said Peleus Uhley, platform security strategist for Adobe, in a blog post.

But plug-ins that automatically update themselves -- and Oracle notably has yet to release such a capability for Java runtime environment or the Java browser plug-in -- and distributing updates through third parties can only go so far. "One of the hardest challenges in protecting end users is reaching what is sometimes referred to as the 'long tail' in an update graph," Uhley said. "These are the users who, for various reasons, have not updated their systems in several months or even years. Reaching these last few end users can be difficult if they have disabled their update mechanisms. Unfortunately, they are also the users who are most likely to be successfully attacked."

Failing to keep plug-ins updated comes at a security cost, since updates often include fixes for known vulnerabilities. On that front, Coates also urged Firefox users to visit a dedicated website "to determine if plug-ins are current."

Getting accurate information on a plug-in, however, isn't always a straightforward process. One of the criticisms recently leveled at Java by security researchers, for example, is that browsers have been incorrectly detecting which version of Java is installed, as well as sometimes altogether misreporting if Java is, or isn't, installed.

Oracle failed to respond to emailed questions, sent earlier this month, about whether fixing those Java installation and version-reporting errors would require an update from Oracle, browser makers or both.