source: https://www.securityfocus.com/bid/15108/info

Gallery is prone to a directory traversal vulnerability. This issue is due to a failure in the application to properly sanitize user-supplied input.

Exploitation of this vulnerability could lead to a loss of confidentiality. Information obtained may aid in further attacks against the underlying system; other attacks are also possible. 

http://example.com/gallery2/main.php?g2_itemId=/../../../../../../../etc/aliases%00