Solaris 2.5.1 and 2.6:
$ ln -s /usr/bin/true /tmp/e
$ PATH=/tmp IFS=x /usr/bin/false
$ echo $?
0
This combined with the habit of giving non-login accounts /bin/false
as a shell feels dangerous.
Credits to Wilhelm Mueller for bringing it up in gnu.bash.bug in the
sense of a security related bug.