The WP Mail SMTP Pro plugin for WordPress is vulnerable to unauthorized access of data due to a missing capability check on the is_print_page function in versions up to, and including, 3.8.0. This makes it possible for unauthenticated attackers to disclose potentially sensitive email information.
https://wpmailsmtp.com/docs/how-to-view-recent-changes-to-the-wp-mail-smtp-plugin-changelog/