Tested it with
NcFTP 2.4.2:
No security problem, the file "|sh" does exists afterwards.
netkit-ftp-0.10:
Problem occurs as described.
Navigator/Communicator:
No security problem, the content of the file is displayed.
>I also wonder about IBM's answer:
>SOLUTION: Remove the setuid bit from the "ftp" command.
>
>On our 4.2.1, ftp will not run if it is not suid.
>Didn't somebody test this?
Yep. ftp does not need suid:
-rwxr-xr-x 1 root root /bin/ftp*
-rwxr-xr-x 1 root root /usr/bin/ncftp*
DFN-CERT corrected the solution of IBM. It was a false statment according to
them.