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.
http://www.vupen.com/english/advisories/2007/4024
http://www.securityfocus.com/bid/26617
http://securitytracker.com/id?1019007