WordPlate makes your WordPress site more secure out of the box. WordPlate comes with the
wp-password-bcrypt package to replace WordPress’s outdated and insecure MD5-based password hashing with the modern and secure bcrypt.
We recommend taking a look at the Soil plugin by Roots. It is a WordPress plugin which contains a collection of modules to apply theme-agnostic front-end modifications. The plugin also address some security concerns for WordPress themes.
We suggest reading this article to learn more about theme security in WordPress.