source: https://www.securityfocus.com/bid/9389/info

This vulnerability may allow and attacker to gain access to files that reside outside of the web root directory using a specially crafted URI that contains URL-encoded variations of directory traversal sequences.

This issue has been reported to affect Windows variants of the software. It is not known if other versions are also affected.

http://www.example.com/%5c%2e%2e%5c%2e%2e%5c%2e%2e%5c%2e%2e%5cboot.ini