Scans your wp-content directory for vulnerable instances of timthumb.php, and optionally upgrades them to a safe version.
The recent Timthumb.php vulnerability (discussed here) has left scores of unsuspecting bloggers hacked. It's the perfect combination of not so easy to fix for the technically disinclined, and easy to find and exploit for the malicious - resulting in a disastrous number of compromised sites.
The Timthumb Vulnerability Scanner plugin will scan your entire wp-content directory for instances of any outdated and insecure version of the timthumb script, and give you the option to automatically upgrade them with a single click. Doing so will protect you from hackers looking to exploit this particular vulnerability.
After new, lesser vulnerabilities were found, it became apparent that the plugin needs to be dynamic - able to keep you up to date with the latest version of timthumb, without requiring a plugin upgrade. The plugin now checks for the latest available version of timthumb routinely (each time you visit the scanner page, but no more than once a day), and can download and install the latest version, rather than the one included with the plugin. Scans are run daily (unless you disable them via the options link on the scanner page) via wp-cron to keep up with any new plugins or themes you've installed.
More info at CodeGarage.
Special thanks to Jacob Gillespie for help with the bulk upgrade feature.