Opera before 10.01 does not properly restrict HTML in a (1) RSS or (2) Atom feed, which allows remote attackers to conduct cross-site scripting (XSS) attacks, and conduct cross-zone scripting attacks involving the Feed Subscription Page to read feeds or create feed subscriptions, via a crafted feed, related to the rendering of the application/rss+xml content type as "scripted content."
http://archives.neohapsis.com/archives/bugtraq/2009-10/0289.html
http://secunia.com/advisories/37182
https://exchange.xforce.ibmcloud.com/vulnerabilities/54021
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6314
http://www.opera.com/docs/changelogs/mac/1001/
http://www.opera.com/docs/changelogs/unix/1001/
http://www.opera.com/docs/changelogs/windows/1001/