Opera 9.52 does not properly handle an IFRAME element with a mailto: URL in its SRC attribute, which allows remote attackers to cause a denial of service (resource consumption) via an HTML document with many IFRAME elements.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11952
http://www.securityfocus.com/archive/1/511327/100/0/threaded
http://lists.opensuse.org/opensuse-security-announce/2010-08/msg00001.html