As you all know WordPress allow us to edit files from the WordPress Admin Dashboad. This is a good feature. But it can be harmful for your website. If any hackers gain access to your WordPress admin panel, they can inject subtle, malicious code to your theme and plugin.
To disable the ability to edit plugins and the theme files, Just paste the following code in your wp-config.php file.
define('DISALLOW_FILE_EDIT', true);