Horde IMP 2.2.4 and earlier allows local users to overwrite files via a symlink attack on a temporary file.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0729
http://www.horde.org/imp/2.2/news.php
http://archives.neohapsis.com/archives/bugtraq/2001-05/0303.html