The news-feed preview feature in Opera before 10.61 does not properly remove scripts, which allows remote attackers to force subscriptions to arbitrary feeds via crafted content.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12073
http://www.opera.com/support/kb/view/968/
http://www.opera.com/docs/changelogs/windows/1061/