Foxfire has added a feature called "click-to-play plugins". If you enable this feature, plugins like Flash and Java must be clicked before the plugin is loaded and runs. The feature, which Mozilla also calls "opt-in activation for plugins" is already accessible in nightly builds of Firefox. They are working on giving the browser the ability to remember the settings on a site by site basis.
If you have a recent build of Firefox, you can try the feature by typing about:config into the browsers address bar. Then enable the " plugins.click_to_play " flag. Once this is enabled, Flash and other content on web pages will only play after the user has clicked on it. This prevents videos on web sites from autoplaying, which can be a nuisance for many users. It also conserves system resources.
The main benefit of the add on is that plugins only load when the user actually clicks on the content. This limits the opportunities for malware attacks by malicious content that targets plugin vulnerabilities in Flash and Java. This feature can help to prevent the spread of malware such as the Flashback trojan, since Java would only be loaded if the user expects legitimate Java content on the page.
More information about opt-in activation for plugins is available on the Mozilla wiki. Nightly builds of Firefox with the new feature included are available from the Mozilla web site for Windows, Mac OS X and Linux.