Compromised third-party apps/scripts silently hijack client storefront checkouts — and agencies can't detect it or date the incident

Summary

Agencies maintaining Shopify/Wix/Webflow storefronts install dozens of third-party apps and embeds per client. When one of those apps is compromised or ships a malicious update, the storefront still looks 'up' — uptime monitors report green — while the checkout is quietly redirected to a spoof domain that swaps the customer's cart and captures payment. The agency only finds out when a client forwards angry customer complaints ('surprise support request'), and even then has no way to know how long the hijack has been live, which clients are affected, or whether the same app version is running on other managed stores. Disabling the embed is trial-and-error forensics done live, under client pressure. This is unsolved: uptime/status tools only check availability, security scanners check the platform, not installed embeds, and no agency-facing layer diffs app/script/embed changes across a multi-platform portfolio and alerts on checkout-path tampering. The business fallout is severe — lost revenue, PCI/trust exposure, and an account manager unable to tell the client anything except 'we're looking into it.'