Mozilla’s plugin check checks and shows update status of all Firefox plugins, this plugin check service is not limited to Firefox, but available to all browsers (update: at present, its only limited to Firefox browser only).
It’s interesting how Google Chrome deals with plugins, Google browser auto-updates flash player whenever security updates to flash player are released. For remaining plugins installed in Chrome, you need to manually check for updates and install them when available.
But do you know, there is an extension developed by Google named Secbrowsing (update: the extension no longer available), which periodically checks for Google Chrome plugin updates and alerts you when plugins are out of date.
UPDATE October 21, 2015: Since Google has removed support for NPAPI plugins, the only plugin you may concerned about nowadays is Flash, which Chrome auto-updates whenever a new version is available.
Yet another plugin checker that doesn’t got the limelight as Mozilla Plugin checker got is Qualys BrowserCheck. This service scans for vulnerabilities in Chrome browser, and its plugins, and shows the browser’s security status.
To use it, visit, Qualys BrowserCheck page
And click on Scan without installing the plugin and check the report and follow the recommendations offered after reviewing them.