source: https://www.securityfocus.com/bid/19907/info

Twiki is prone to a directory-traversal vulnerability because it fails to properly sanitize user-supplied input. 

An attacker can exploit this vulnerability to retrieve arbitrary files from the vulnerable system in the context of the affected application. Information obtained may aid in further attacks.

Twiki versions 4.00 to 4.04 are vulnerable to this issue.

http://example.com/bin/viewfile/TWiki/TWikiDocGraphics?rev=1;filename=../../../../../etc/passwd