A set of directives by the EU to make online payment transactions more secure and reduce fraud. Some of those directives impact UX, including 3DS requirements, which is a form of 2fa for payments.
It is the Revised Payment Services Directive requirements for Strong Customer Authentication. An EU directive that applies to credit cards issued by EU merchant banks for transactions that occur within the European Economic Area.
Basically a popup that will request some extra form of security verification for relevant transactions.