Cross-site scripting (XSS) vulnerability in the redirect function in functions.php in MyBB (aka MyBulletinBoard) 1.4.2 allows remote attackers to inject arbitrary web script or HTML via the url parameter in a removesubscriptions action to moderation.php, related to use of the ajax option to request a JavaScript redirect.  NOTE: this can be leveraged to execute PHP code and bypass cross-site request forgery (CSRF) protection.