Tol1

В pluggable.php строка 876
header("Location: $location", true, $status);
а это кусок кода из которого она (3-я снизу)

function wp_redirect($location, $status = 302) {
	global $is_IIS;

	$location = apply_filters('wp_redirect', $location, $status);
	$status = apply_filters('wp_redirect_status', $status, $location);

	if ( !$location ) // allows the wp_redirect filter to cancel a redirect
		return false;

	$location = wp_sanitize_redirect($location);

	if ( !$is_IIS && php_sapi_name() != 'cgi-fcgi' )
		status_header($status); // This causes problems on IIS and some FastCGI setups

	header("Location: $location", true, $status);
}
endif;