Opera 9.52 allows remote attackers to cause a denial of service (resource consumption) via JavaScript code containing an infinite loop that creates IFRAME elements for invalid (1) news:// or (2) nntp:// URIs.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11622
http://www.securityfocus.com/archive/1/511509/100/0/threaded