Cross-site scripting (XSS) vulnerability in Opera 9 and 10 allows remote attackers to inject arbitrary web script or HTML via a (1) RSS or (2) Atom feed, related to the rendering of the application/rss+xml content type as "scripted content." NOTE: the vendor reportedly considers this behavior a "design feature," not a vulnerability.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6370
http://www.securityfocus.com/archive/1/506517/100/0/threaded