The Subscribe2 plugin for WordPress is vulnerable to unauthorized access to email functionality due to a missing capability check when sending test emails in versions up to, and including, 10.40. This makes it possible for author-level attackers to send emails with arbitrary content and attachments to site users.
https://plugins.trac.wordpress.org/changeset/2930676
https://plugins.trac.wordpress.org/browser/subscribe2/trunk/admin/send-email.php#L12