Comments popup broken on upgrade to 4.5.2

Have you tried:
-deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).
-switching to the default theme to rule out any theme-specific problems.

Turns out we weren’t at 4.5.1 as believed but 4.4.2 and comments popups were deprecated in 4.5.0. I still need them, though, so I guess I’ll have to figure out how to put them back in. Any suggestions or pointers would be appreciated.

You should upgrade as soon as possible for security reasons.

Issue resolved. Added template_include filter to functions:

add_filter( 'template_include', 'comments_popup_template', 99 );

function comments_popup_template( $template ) {

	if( isset($_GET['comments_popup']) && $_GET['comments_popup'] != '')
	{
		$new_template = locate_template( array( 'comments-popup.php' ) );
		if ( '' != $new_template ) {
		return $new_template ;
		}
	}
	return $template;
}

I just had this happen when I upgraded to 4.7.2. Popups do not work on any theme when enabled. You say to add the script above to the functions. Which functions? Theme_functions, or different one?

I added it to functions.php in my theme directory.