The Newsletters plugin for WordPress is vulnerable to blind SQL Injection via the 'user_email' parameter in all versions up to, and including, 4.18.2 due to insufficient escaping on the user supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for authenticated attackers, with subscriber-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database. Exploitation requires the admin-controlled 'currentusersubscribed' option to be enabled and at least one page rendering the Newsletters subscribe shortcode or widget to exist; a Subscriber-level attacker can self-serve the attack by updating their own profile email to a crafted payload and loading such a page.