KDE allows local users to execute arbitrary commands by setting the KDEDIR environmental variable to modify the search path that KDE uses to locate its executables.
KMail in KDE 1.0 provides a PGP passphrase as a command line argument to other programs, which could allow local users to obtain the passphrase and compromise the PGP keys of other users by viewing the arguments via programs that list process information, such as ps.
KDE file manager (kfm) uses a TCP server for certain file operations, which allows remote attackers to modify arbitrary files by sending a copy command to the server.