Opera before 10.63 does not properly select the security context of JavaScript code associated with an error page, which allows user-assisted remote attackers to conduct cross-site scripting (XSS) attacks via a crafted web site.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12115
http://www.opera.com/support/kb/view/976/
http://www.opera.com/docs/changelogs/windows/1063/
http://www.opera.com/docs/changelogs/unix/1063/
http://www.opera.com/docs/changelogs/mac/1063/