Prevent your site from being clickjacked with this plugin that includes the X-Frame-Options SAMEORIGIN and a modified version of OWASP's legacy browser frame breaking script. The OWASP's legacy browser frame breaking script is modified to work in browsers without Javascript (as well as browsers with Javascript). This additional script prevents other sites from putting your site in an iFrame for security reasons.
You can read more about clickjacking defense on
OWASP
Additional Details
If you'd like to disable the clickjacking JavaScript on a page you can use this filter in your theme's functions.php file.
add_filter('wp_anti_clickjack', '__return_false' );
If you'd like to disable the clickjacking X-Frame-Options HTTP header you can use this filter in your theme's functions.php file.
add_filter('wp_anti_clickjack_x_frame_options_header', '__return_false' );