Paypal Not Working - frame issue

This is what customer is getting:
When I get to page to put in my credit card # This content cannot be displayed in a frame

To help protect the security of information you enter into this website, the publisher of this content does not allow it to be displayed in a frame.
I tried this fix below:

Edit the file plugins/hikashoppayment/paypal/paypal_end.php and change the line:
<form id="hikashop_paypal_form" name="hikashop_paypal_form" action="<?php echo $method->payment_params->url;?>" method="post">

to:
<form id="hikashop_paypal_form" name="hikashop_paypal_form" action="<?php echo $method->payment_params->url;?>" method="post" target="_blank">

But then the popup blocker blocks it and it does not work. Several customers are experiencing this.

You can potentially try with that code instead but it might not be enough :
<form id="hikashop_paypal_form" name="hikashop_paypal_form" action="<?php echo $method->payment_params->url;?>" method="post" target="_top">

Unfortunately, there is no magic bullet on our end.
That error is because your website is displayed inside a frame by your hosting/a CDN/a caching provider/an add company/an extension in order for example to add an ad banner at the top/bottom.
Because of that PayPal refuses the payment in order to avoid scams/fishing technics which can use that method in order to trick users into sending them money.
So your best solution is to remove the thing which adds the frame around your website.