Payment-page integrity is the set of controls that verify checkout scripts, tags, and related browser-side code have not been changed without authorization. It focuses on the page the customer actually loads, not only the backend systems behind it. Typical checks include script allowlisting, file hashing, content security policy enforcement, dependency monitoring, and tight change control for third-party code.
This matters because many card-stealing attacks inject or replace JavaScript on checkout pages to capture card numbers, names, or CVV data before the payment reaches the processor. If integrity controls are weak, a malicious script can blend into a legitimate storefront and silently exfiltrate data from the browser. Defenders use integrity monitoring, code review, and alerts on unexpected script changes to catch e-skimming and other browser-side theft. In practice, payment-page integrity turns the checkout page into a monitored security boundary, where even small unauthorized edits become visible.