Proxy Check is a tool that includes a website to automate testing for web proxy content filtering. It has a battery of tests that includes looking for typically malicious URLs, several PDF exploits, and more.
You can download it from the following link: https://packetstormsecurity.com/files/download/111015/proxycheck-02122011.tgz
Source: https://packetstormsecurity.com/files/111015/Proxy-Check-02122011.html