Mozilla released a fix for the latest version of Firefox across all platforms including Windows, Mac, Linux and Android. You can download this update manually, though you shouldn't have to do anything if you have automatic updates enabled. This particular issue doesn't affect users running an older version of the browser.
Firefox 16's new developer command line
Security blunder aside, Firefox 16 brings many improvements over August's build, including improved support for Mac OS X Lion, the introduction of incremental garbage collection, a greater implementation of HTML5 and CSS3, a developer command line, a Reader Mode for Android and more bug fixes than we care to count.