PayPal allows its payment pages to appear inside a frame only for the following products:
Due to security concerns, the browser must be current and secure for iFrame use.
Transactions involving users on certain browsers or older versions of browsers shouldn't use the iFrame flow.
Note: If the PayPal iFrame becomes the source of an attack, the attack would appear to originate from the merchant site. To avoid this additional risk, don’t use an iFrame flow.