CVE 2010-4536
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.
See the 
CVE page on Mitre.org
for more details.
