buttonpressed.sh in scanbuttond 0.2.3 allows local users to overwrite arbitrary files via a symlink attack on the (1) scan.pnm and (2) scan.jpg temporary files.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2007-6100
https://bugzilla.redhat.com/show_bug.cgi?id=383131
http://www.vupen.com/english/advisories/2007/4024
http://www.securityfocus.com/bid/26617
http://securitytracker.com/id?1019007