Mozilla Firefox before 3.6 Beta 3 does not properly handle overlong UTF-8 encoding, which makes it easier for remote attackers to bypass cross-site scripting (XSS) protection mechanisms via a crafted string, a different vulnerability than CVE-2010-1210.
http://hg.mozilla.org/releases/mozilla-1.9.2/rev/e42c563313a0
http://sirdarckcat.blogspot.com/2009/10/couple-of-unicode-issues-on-php-and.html