Today Mozilla announced that Firefox will soon block most third-party plugins by default.
A plugin is 3rd-party software which is loaded into the browser to assist in rendering the Web. Even though many users are not even aware of plugins, they are a significant source of hangs, crashes, and security incidents. By allowing users to decide which sites need to use plugins, Firefox will help protect them and keep their browser running smoothly.
The one plugin not affected by this change is Flash, which will remain enabled by default. Flash content is so common on the Web, and many websites use “hidden” Flash instances that the user does not see and cannot click on: making Flash click-to-play would be confusing for most users. Users with older versions of Flash that are known to be insecure will see the click-to-activate UI and will be prompted to upgrade to the latest version. Our security and plugin teams work closely with Adobe to make sure that Firefox users are protected from instability or security issues in the Flash plugin