Interpretation conflict in Drupal 4.7.x before 4.7.11 and 5.x before 5.6, when Internet Explorer 6 is used, allows remote attackers to conduct cross-site scripting (XSS) attacks via invalid UTF-8 byte sequences, which are not processed as UTF-8 by Drupal's HTML filtering, but are processed as UTF-8 by Internet Explorer, effectively removing characters from the document and defeating the HTML protection mechanism.
https://exchange.xforce.ibmcloud.com/vulnerabilities/39619
http://www.vupen.com/english/advisories/2008/0134
http://www.vupen.com/english/advisories/2008/0127
http://www.vbdrupal.org/forum/showthread.php?t=1349
http://www.vbdrupal.org/forum/showthread.php?p=6878
http://www.securityfocus.com/bid/27238
http://secunia.com/advisories/28486