[BUG] Payment of unpaid orders renders the page incorrectly

-- HikaShop version -- : 3.1.1
-- Joomla version -- : 3.7.2
-- PHP version -- : 5.6.30

Hi! I'm the developer of several HS payment plugins, you can check them here www.mgscreativa.com/en/online-store/more-products/hikashop

A customer recently contacted me for a strange page render issue in our Blockchian payment plugin. The issue arises when an user wants to pay an unpaid order.

The issue basically renders the payment plugin HTML code on top of the rest of the page HTML code, including the HTML and BODY tags!. Please see attachment

After a complete review of the plugin code, I can't see any mistakes, and after reviewing the code of the order controller I see that the code gets echoed from the result of onAfterOrderConfirm which in my case returns the result fo calling the 'end' plugin template

    ...
    $this->vars = $vars;
    return $this->showPage('end');
    ...

Done!

Done, it fixes the issue!

			ob_start();
			if(method_exists($paymentPlugin, 'onAfterOrderConfirm'))
				$paymentPlugin->onAfterOrderConfirm($order, $paymentMethods, $order->order_payment_id);

			$html = ob_get_clean();