The to-upgrade plugin in feta 1.4.16 allows local users to overwrite arbitrary files via a symlink on the (1) /tmp/feta.install.$USER and (2) /tmp/feta.avail.$USER temporary files.
https://bugs.gentoo.org/show_bug.cgi?id=235770
http://www.securityfocus.com/bid/30899
http://www.openwall.com/lists/oss-security/2008/10/30/2
http://www.debian.org/security/2008/dsa-1643
http://secunia.com/advisories/32155