The Mozilla Foundation has published a
Plugin Check for web browser plug-ins. Just by visiting the web site you can immediately see if your plug-ins are up-to-date (green), outdated but without known vulnerabilities (yellow) or if they are known to have security holes and are outdated (red).
The check is supposed to work for Java, Adobe Reader, Flash, Shockwave, QuickTime, Windows Media Player and DivX. Supported operating systems are Windows, Mac OS X and Linux. If a plug-in is outdated, you can click on the button next to it to be sent to the manufacturer’s homepage and fetch the update.