Opera before 11.65 does not ensure that keyboard sequences are associated with a visible window, which makes it easier for user-assisted remote attackers to conduct cross-site scripting (XSS) attacks or execute arbitrary code via a crafted web site, related to a "hidden keyboard navigation" issue.
http://www.opera.com/support/kb/view/1021/
http://www.opera.com/docs/changelogs/windows/1200/
http://www.opera.com/docs/changelogs/unix/1200/