In the module "PayPal Official" for PrestaShop 7+ releases prior to version 6.4.2 and for PrestaShop 1.6 releases prior to version 3.18.1, a malicious customer can confirm an order even if payment is finally declined by PayPal. A logical weakness during the capture of a payment in case of disabled webhooks can be exploited to create an accepted order. This could allow a threat actor to confirm an order with a fraudulent payment support. Versions 6.4.2 and 3.18.1 contain a patch for the issue. Additionally, users enable webhooks and check they are callable.
https://github.com/202ecommerce/paypal/security/advisories/GHSA-w3w3-j3mh-3354