Hello, @marianogi,
First of all, Thanks for the detailed explanation of your issue. I can understand the importance of website security. I am glad to tell you that our theme is compatible with the “Nextend Social Login and Register” plugin you can try to use this plugin and I hope it works fine for you. Here is the link to the plugin: https://wordpress.org/plugins/nextend-facebook-connect/
Simply download and install the plugin on your site. But Please take a complete backup of your site first. Further, here is the plugin documentation link to understand how to configure the plugin settings and how it works on the site: https://nextendweb.com/nextend-social-login-docs/documentation/
Best Regards,
PThemes Team.