MailEnable < 10.54 Reflected XSS in WindowContext Parameter of MAI/compose.aspx

MailEnable versions prior to 10.54 contain a reflected cross-site scripting (XSS) vulnerability in the WindowContext parameter of /Mondo/lang/sys/Forms/MAI/compose.aspx. The WindowContext value is not properly sanitized when processed via a GET request and is reflected within a <script> context in the JavaScript variable window.location, allowing an attacker to break out of the existing script and inject arbitrary JavaScript. A remote attacker can supply a crafted payload that terminates the existing ProcessContextSwitchResult() function, inserts attacker-controlled script, and comments out remaining code, leading to script execution in a victim’s browser when the victim visits a malicious link or attempts to send an email. Successful exploitation can redirect victims to malicious sites, steal non-HttpOnly cookies, inject arbitrary HTML or CSS, and perform actions as the authenticated user.