WordPress Core versions up to 6.0.3 had a security issue with how they handled user permissions. This fix was made to address two vulnerabilities in wp-mail.php and wp-trackback.php which could have allowed for malicious cross-site scripting and request forgeries. The previous setup could have allowed third-party plugins or themes to use the wp_set_current_user function incorrectly, making it possible for users to gain more permissions than intended.