The SPICE Firefox plug-in (spice-xpi) 2.4, 2.3, 2.2, and possibly other versions allows local users to overwrite arbitrary files via a symlink attack on the usbrdrctl log file, which has a predictable name.
https://bugzilla.redhat.com/show_bug.cgi?id=639869
http://www.vupen.com/english/advisories/2011/0899
http://www.securitytracker.com/id?1025304