Opera before 10.63 does not properly restrict web script in unspecified circumstances involving reloads and redirects, which allows remote attackers to spoof the Address Bar, conduct cross-site scripting (XSS) attacks, and possibly execute arbitrary code by leveraging the ability of a script to interact with a web page from (1) a different domain or (2) a different security context.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12071
http://www.opera.com/support/kb/view/973/
http://www.opera.com/docs/changelogs/windows/1063/
http://www.opera.com/docs/changelogs/unix/1063/
http://www.opera.com/docs/changelogs/mac/1063/