Opera before 9.26 allows remote attackers to "bypass sanitization filters" and conduct cross-site scripting (XSS) attacks via crafted attribute values in an XML document, which are not properly handled during DOM presentation.
http://www.vupen.com/english/advisories/2008/0622
http://www.securityfocus.com/bid/27901
http://www.opera.com/support/search/view/880/
http://www.opera.com/docs/changelogs/linux/926/
http://security.gentoo.org/glsa/glsa-200803-09.xml
http://secunia.com/advisories/29178
http://secunia.com/advisories/29152
http://secunia.com/advisories/29029
http://lists.opensuse.org/opensuse-security-announce/2008-02/msg00010.html