Interpretation conflict in PostNuke 0.761 and earlier allows remote attackers to conduct cross-site scripting (XSS) attacks via HTML tags with a trailing "<" character, which is interpreted as a ">" character by some web browsers but bypasses the blacklist protection in (1) the pnVarCleanFromInput function in pnAPI.php, (2) the pnSecureInput function in pnAntiCracker.php, and (3) the htmltext parameter in an edituser operation to user.php.