XST Strikes Back – A technical paper discussing Cross Site Tracing vulnerabilities in proxy servers.
You can download it from the following link: https://packetstormsecurity.com/files/download/43425/XST_strinkes_back.txt
Source: https://packetstormsecurity.com/files/43425/XST-Strikes-Back-Cross-Site-Tracing-Whitepaper.html