SSL Zen <= 4.5.3 - Unauthenticated Private Keys Access

The SSL Zen WordPress plugin before 4.6.0 does not properly prevent directory listing of the private keys folder, as it only relies on the use of .htaccess to prevent visitors from accessing the site's generated private keys, which allows an attacker to read them if the site runs on a server who doesn't support .htaccess files, like NGINX.