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In today’s e-commerce world, a single overlooked script can quietly leak your customers’ card data and wreck years of brand trust.
When a customer reaches your checkout page, it’s not just your own code running it’s a patchwork of scripts: analytics platforms, personalization engines, ad trackers, chat widgets, and more. Each was added for a good reason: to increase conversions, help marketing, or improve customer support.
But here’s the catch: every single script you add to that page can read, modify, or even capture sensitive cardholder data as it’s typed. And attackers know it.
Over the last decade, the risk moved from theory to reality.
Groups like Magecart turned these everyday scripts into weapons. By quietly injecting malicious code into payment pages, they skimmed card data straight from users’ browsers without ever touching the server.
Because these attacks run on client-side, they’re invisible to traditional defences like firewalls, server monitoring, or antivirus.
The convenience that made scripts so popular quick to deploy, easy to update, running entirely in the browser is the very thing that makes them dangerous. And that’s why PCI DSS v4.0.1 now demands businesses stop trusting scripts blindly and start controlling exactly what’s allowed to run, why it’s needed, and whether it stays safe.
Not long ago, payment security felt mostly like a server-side problem: keep your database patched, protect your network, and you’d be reasonably safe. Magecart changed all that.
Instead of attacking your servers directly, Magecart-style attackers target the browser itself. They find ways to inject malicious scripts often by compromising a third-party vendor, hijacking a content delivery network (CDN), or tricking someone into adding a seemingly harmless script. Once injected, the script quietly captures card details as customers type them into the checkout page.
Because this happens entirely in the browser, traditional defences like firewalls, WAFs, and server monitoring tools don’t pick it up. Worse still, the customer never knows: the page looks and functions exactly as intended while sensitive data is silently siphoned off in real time.
These aren’t rare edge cases, either. Many of these attacks stem not from highly advanced techniques, but from neglected or outdated scripts that were never reviewed or properly controlled.
The lesson? Payment page scripts don’t just support your business they can also silently destroy customer trust if left unchecked. That’s exactly why PCI DSS v4.0.1 introduced Requirement 6.4.3: to bring visibility, control, and security back to the browser.
At its heart, Requirement 6.4.3 is simple: don’t just hope your payment page scripts behave - control them, prove why they’re there, and keep them trustworthy.
Here’s what PCI DSS v4.0.1 expects you to actually do:
Altogether, these steps turn your scripts from an overlooked risk into something you can manage, track, and prove is secure not just once for an audit, but every day.
It’s easy to read Requirement 6.4.3 and think, “Great, another list to maintain.” But the real point isn’t paperwork it’s to keep your payment page safe without breaking your site or slowing your teams.
The real key isn’t adding dozens of new tools, it’s having clear visibility. Knowing what scripts you have, why they’re there, and proving they stay trusted. Once that becomes part of your process, compliance becomes far less painful and far more effective.
Web-skimming and script-based attacks have emerged as a major concern for
e-commerce businesses. These breaches often go undetected for extended periods because the malicious code operates in the customer’s browser far from traditional server-side security controls.
What’s especially troubling is that many of these attacks originate from third-party scripts added in good faith but never reviewed or maintained. It’s not always sophisticated threat actors breaking through firewalls sometimes, it’s simply an old script that no one realized was still running.
That’s why visibility, verification, and control are essential not just for compliance, but to protect customer trust and long-term business reputation.
Protecting your checkout page shouldn’t mean drowning in spreadsheets, blocking your marketing team, or worrying every time someone adds a new script. At Crossbow, our role is to help you make PCI DSS v4.0.1 something your team can actually live with and keep it working as your site evolves.
Here’s how we help turn Requirement 6.4.3 from theory into practice:
We don’t just list the requirements we help you understand, apply, and maintain them, so payment page security becomes part of your normal process.
