International Components for Unicode (ICU) 4.0, 3.6, and other 3.x versions, as used in Apple Mac OS X 10.5 before 10.5.7, iPhone OS 1.0 through 2.2.1, iPhone OS for iPod touch 1.1 through 2.2.1, Fedora 9 and 10, and possibly other operating systems, does not properly handle invalid byte sequences during Unicode conversion, which might allow remote attackers to conduct cross-site scripting (XSS) attacks.