GNU Parallel before 20150422, when using (1) --pipe, (2) --tmux, (3) --cat, (4) --fifo, or (5) --compress, allows local users to write to arbitrary files via a symlink attack on a temporary file.

GNU Parallel before 20150522 (Nepal), when using (1) --cat or (2) --fifo with --sshlogin, allows local users to write to arbitrary files via a symlink attack on a temporary file.