Opera before 11.65 does not properly restrict the reading of JSON strings, which allows remote attackers to perform cross-domain loading of JSON resources and consequently obtain sensitive information via a crafted web site.
http://www.opera.com/support/kb/view/1019/
http://www.opera.com/docs/changelogs/windows/1200/
http://www.opera.com/docs/changelogs/unix/1200/