Update the WordPress MailerLite – Signup forms plugin to the latest available version (at least 1.5.8).
Muhammad Daffa discovered and reported this Cross Site Request Forgery (CSRF) vulnerability in WordPress MailerLite – Signup forms Plugin. This could allow a malicious actor to force higher privileged users to execute unwanted actions under their current authentication. This vulnerability has been fixed in version 1.5.8.