Magecart attacks involve injecting malicious JavaScript into eCommerce websites to steal payment card data. These attacks often target third-party scripts and supply chain vulnerabilities. Prevention requires vigilant monitoring of third-party resources, implementing CSP, regular security scanning, and maintaining secure coding practices.
Attackers rarely breach the store directly. Instead they compromise something the checkout page already trusts, a third-party script like an analytics tag, a chat widget, or a payment library hosted on a CDN, and add a few lines of skimming code to it. When the page loads that script, the skimmer runs in every shopper's browser, listens to the card and address fields, and quietly sends a copy of each entry to an attacker-controlled domain. Because the theft happens in the browser, server logs and traditional web application firewalls see nothing unusual.
The malicious code lives on a legitimate, allow-listed domain, so a Content Security Policy that trusts that domain will happily execute it. Skimmers also cloak themselves: they check for developer tools, only fire on checkout URLs, and rotate exfiltration domains to evade blocklists. Many campaigns run for months before discovery, and each one puts the merchant on the hook for PCI DSS penalties, card-brand fines, and forced forensic audits.
cside fetches third-party scripts on our side with the Script Method and analyses the actual JavaScript payload before it executes in the shopper's browser, rather than trusting a script by its source domain. A skimmer injected into an allow-listed vendor script is caught by what the code does, reading card fields or contacting an unfamiliar domain, not by where it came from. When something malicious appears, cside can block it in real time and keeps a forensic record of the exact code that ran, which is what PCI DSS 6.4.3 and 11.6.1 require you to demonstrate.
A server-side breach steals data at rest from a database or backend. Magecart steals it in motion, in the shopper's browser, at the moment of entry, before the data ever reaches your server. That is why server-side tools and WAFs often miss it entirely, and why detection has to happen on the client side.
Not reliably. A CSP restricts which domains can load scripts, but Magecart usually hides inside a script served from a domain you already trust and allow-list. Once that vendor is compromised, the CSP treats the skimmer as legitimate. You need payload-level inspection of what each script actually does, not just where it loads from.
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