Opera before 8.51 on Linux and Unix systems allows remote attackers to execute arbitrary code via shell metacharacters (backticks) in a URL that another product provides in a command line argument when launching Opera.
http://www.novell.com/linux/security/advisories/2005_28_sr.html
https://euvd.enisa.europa.eu/vulnerability/EUVD-2005-3745
http://www.vupen.com/english/advisories/2005/2519
http://www.securityfocus.com/bid/15521
http://www.securityfocus.com/archive/1/417393/30/0/threaded
http://www.opera.com/docs/changelogs/linux/851/
http://securitytracker.com/id?1015253
http://secunia.com/secunia_research/2005-57/advisory/
http://secunia.com/advisories/18111
http://secunia.com/advisories/16907
http://archives.neohapsis.com/archives/fulldisclosure/2005-11/0677.html