Multiple cross-site scripting (XSS) vulnerabilities in KSES, as used in WordPress before 3.0.4, allow remote attackers to inject arbitrary web script or HTML via vectors related to (1) the & (ampersand) character, (2) the case of an attribute name, (3) a padded entity, and (4) an entity that is not in normalized form.
http://www.vupen.com/english/advisories/2011/0167
http://www.vupen.com/english/advisories/2010/3335
http://www.securityfocus.com/bid/45620
http://www.openwall.com/lists/oss-security/2010/12/30/1
http://wordpress.org/news/2010/12/3-0-4-update/
http://secunia.com/advisories/43000
http://secunia.com/advisories/42755
http://lists.fedoraproject.org/pipermail/package-announce/2011-January/053293.html
http://lists.fedoraproject.org/pipermail/package-announce/2011-January/053289.html