Opera before 11.65 does not ensure that the address field corresponds to the displayed web page during blocked navigation, which makes it easier for remote attackers to conduct spoofing attacks by detecting and preventing attempts to load a different web page.
http://www.opera.com/support/kb/view/1022/
http://www.opera.com/docs/changelogs/windows/1200/
http://www.opera.com/docs/changelogs/unix/1200/
http://www.opera.com/docs/changelogs/mac/1200/
http://www.opera.com/docs/changelogs/mac/1165/
http://blog.vulnhunt.com/index.php/2012/06/14/cal-2012-0015-opera-website-spoof/