The (1) settings.php and (2) subscribers.php scripts in Open Newsletter 2.5 and earlier do not exit when authentication fails, which allows remote attackers to perform unauthorized administrative actions, or execute arbitrary code in conjunction with another vulnerability.

Open Newsletter 2.5 and earlier allows remote authenticated administrators to execute arbitrary PHP code by inserting the code into the email parameter to (1) subscribe.php or (2) unsubscribe.php.

Cross-site scripting (XSS) vulnerability in compose.php in OpenNewsletter 2.5 and earlier allows remote attackers to inject arbitrary web script or HTML via the type parameter.