Wallos: Authenticated SSRF via per-user SMTP notification host (low-privilege user)

Wallos is an open-source, self-hostable personal subscription tracker. From version 2.0.0 to before version 5.0.0, any authenticated Wallos user (no admin rights required) can make the server open arbitrary outbound SMTP connections to internal/link-local addresses, by setting the SMTP host of their personal email notifications to an internal IP. The per-user notification settings endpoint (endpoints/notifications/saveemailnotifications.php) performs no SSRF validation, and the notification cron (endpoints/cronjobs/sendnotifications.php) feeds that user-controlled host straight into PHPMailer ($mail->Host = $email['smtpAddress']). When the user's subscription notification fires, the server connects to the chosen host:port. This issue has been patched in version 5.0.0.