If you have the Joomla HTTP Headers Plugin enabled with its default settings, the PayPal Checkout popup windows will be blocked. Users will see a blank popup, in some cases with "about:blank#blocked" in the address bar. For PayPal Checkout to work correctly with the Joomla HTTP Headers Plugin enabled, you will need to set the following options:
| Option | Setting |
|---|---|
| Referrer-Policy | strict-origin-when-cross-origin |
| Cross-Origin-Opener-Policy | same-origin-allow-popups |