SmarterTools SmarterMail before 13.3.5535 was vulnerable to stored XSS by bypassing the anti-XSS mechanisms. It was possible to run JavaScript code when a victim user opens or replies to the attacker's email, which contained a malicious payload. Therefore, users' passwords could be reset by using an XSS attack, as the password reset page did not need the current password.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.