Formjacking Meaning
Imagine visiting your favorite e-commerce site, entering your credit card details to make a purchase—and unknowingly handing your information over to a hacker. That’s formjacking in action.
So, what is formjacking attack exactly?
Formjacking is a cyberattack technique where malicious JavaScript code is injected into online forms to steal sensitive user data—most often from checkout pages or payment forms. Unlike malware or phishing, formjacking doesn’t need to infect your device. Instead, it hijacks the form’s backend, quietly intercepting the data before it’s submitted to the legitimate server.
The real danger lies in its invisibility. Users continue shopping unaware, and businesses continue operating with a false sense of security. This makes formjacking one of the most stealthy and damaging web-based attacks.
Formjacking vs. Ransomware
While both are harmful, formjacking is sneakier:
FeatureFormjackingRansomware
ObjectiveData theftData encryption for ransomDetectionHard to detectOften detected post-encryptionVisibilityLow (covert)High (disruptive)ImpactData breach, financial lossOperational disruption, extortionUser ExperienceSite functions normallyLocked systems or data
Formjacking vs ransomware isn’t about which is worse—it’s about knowing that both require distinct strategies. Ransomware is a battering ram; formjacking is a scalpel. But both can cut deep.
Formjacking is silent, sneaky, and often invisible until the damage is done—which is why awareness and proactive formjacking protection are essential.
The Formjacking Threat
Formjacking may seem niche compared to ransomware or phishing, but its impact can be just as devastating. The consequences ripple across financial, legal, and reputational dimensions.
Financial theft: Attackers steal credit card details and it is often used immediately for fraudulent purchases or resold on dark web marketplaces.
Reputation damage: When customers find out that their sensitive user information was compromised on your site, trust erodes fast.
Regulatory penalties: Under laws like GDPR, CCPA, or PCI DSS, failure to protect user data can lead to substantial fines.
Attackers favor formjacking attacks because of its low cost, low risk, and high reward. It doesn’t require extensive infrastructure. Just a single line of malicious code hidden in a checkout script can compromise thousands of customers.
The threat isn’t going away anytime soon. As more services move online and digital transactions grow, formjacking becomes an increasingly attractive tool for attackers.
How Formjacking Happens – A Step-by-Step Breakdown
After getting the answer to the question – What is formjacking? you must be wondering how it occurs. So, at its core, formjacking is deceptively simple: inject malicious code, grab user data, and get out—quietly. But behind that simplicity is a carefully staged attack that plays out in the background of a perfectly normal-looking website. Here’s how it all goes down.
Step 1: Find the Entry Point
The first thing an attacker needs is access. Injecting malicious code into webpage forms requires identifying a vulnerability in the web application. And unfortunately, websites offer plenty of it. Most formjacking attacks begin by exploiting one or more of the following vulnerabilities:
Outdated CMS platforms like WordPress, Joomla, or Magento. Insecure third-party plugins and scripts that are easy to compromise. Poor code hygiene—improper script validation or configuration flaws. Weak permission settings that allow external changes without proper checks.
Sometimes, it’s not even your code that’s the problem—it’s someone else’s. In supply chain attacks, threat actors inject malicious scripts into third-party services or libraries that your site relies on (like analytics tools or shopping cart software). This tactic allows them to compromise hundreds of websites in one go—without directly touching yours.
Step 2: Inject the Malicious Script
Once inside, attackers inject a lightweight, malicious JavaScript code snippet into the site’s source code. These scripts are sneaky by design—they blend in with the rest of your code, using encoded variables, dynamic loading, or logic that only runs on specific pages.
In many cases, these scripts are hosted on external servers. That means even if you do a local code audit, the actual payload might not show up because it’s being pulled from a remote domain. In some cases, malicious code is disguised as a google tag or as a domain that sounds related to the website or payment processor.
Some attackers go a step further and add logic that limits when and where the script runs—maybe it only activates on the payment page, or only for users in the U.S. This helps the attack stay under the radar longer.
Step 3: Monitor Form Activity
With the script in place, the attacker begins quietly watching form fields. They specifically look for inputs like:
Credit card numbers CVV and expiration dates Email IDs and phone numbers Billing addresses and zip codes
This is usually done via DOM manipulation, where the script observes form field values as the user types—before they ever hit “Submit.”
Step 4: Exfiltrate the Data
The moment the user hits submit, their data is intercepted. It’s not sent to the legitimate server right away—instead, a copy is silently sent to a domain controlled by the attacker. The data is often:
Base64 encoded or encrypted Routed through proxy servers Tagged with user metadata like browser type or geolocation
All this happens in real time, without triggering alerts, pop-ups, or visual errors. To the user—and often the website owner—everything appears normal.
Bonus: Persistent & Evasive Behavior
To make things even trickier, attackers often ensure their malicious code persists across updates or reloads. They’ll hook into trusted scripts or use CDN links to keep their payload alive.
This is exactly what groups like Magecart have done in large-scale campaigns—injecting malicious code into shopping cart plugins and third-party libraries to skim credit card details from thousands of unsuspecting sites globally.
From surface mapping to incident prioritization—this checklist has it all.
Map your organization’s threat surface
Detect anomalies in real time
Prioritize high-risk vulnerabilities
How to Detect Formjacking Code?
Fidelis Security has long emphasized the importance of real-time visibility and deception-based detection to uncover hidden threats like formjacking attacks before they escalate.
Detecting formjacking is notoriously difficult. Here’s why it’s such a challenging threat to uncover:
The script is often obfuscated. Attackers use encoding, encryption, or nested functions to hide their logic.
Minimal behavior change. The site continues to work exactly as expected.
No user-side malware. Traditional endpoint protection tools won’t flag anything.
However, some effective detection strategies include:
Content Security Policy (CSP) monitoring: Helps identify attempts to load scripts from unauthorized domains. CSP violation reports can be used as an early warning.
Subresource Integrity (SRI): Verifies that third-party scripts haven’t been altered by checking cryptographic hashes.
Webpage integrity monitoring: Tracks changes in critical form fields, JavaScript files, and DOM structures.
Behavioral analysis and anomaly detection: Watches for unusual outbound requests, especially from forms that handle sensitive data.
In addition, integrating honeypot fields—invisible form fields that real users never fill—can help identify bots or scripts trying to harvest data. If a hidden field is populated, it’s likely the form is being tampered with.
Formjacking may be stealthy, but with layered monitoring and active scanning, it can be caught before damage escalates.
How to Prevent Formjacking?
A proactive defense strategy for formjacking prevention can act as a critical early warning system for formjacking attempts and credential theft.
If you’re wondering about the measure of formjacking prevention, the answer lies in a defense-in-depth approach that spans development, operations, and security.
Here are actionable steps:
Enforce a strict CSP: Only allow scripts from trusted sources. This limits attackers’ ability to load external JavaScript.
Implement SRI for all third-party scripts: This ensures code integrity and flags unauthorized changes.
Minimize third-party dependencies: The more external code you rely on, the larger your attack surface.
Use a Web Application Firewall (WAF): Advanced WAFs can spot script injections or suspicious behavior in form fields.
Keep everything updated: From CMS platforms to plugins and custom scripts, updates often contain security patches.
Perform continuous DOM and source code monitoring: Look for unauthorized changes, especially on sensitive pages.
Scan outbound traffic for anomalies: Use network analytics to detect exfiltration attempts to unusual domains.
Security teams should also practice regular threat modeling. Identify which forms collect sensitive data, who maintains them, and what third-party services they rely on. Only then can you effectively mitigate the threat.
Learn how to create proactive cybersecurity strategies.
Align security with MITRE ATT&CK
Prioritize threats by behavior
Strengthen overall detection posture
The Impact of Formjacking Attacks
Organizations using deception technology from vendors like Fidelis Security are better positioned to detect early signs of exfiltration and mitigate the blast radius of a successful attack.
The fallout from a formjacking attack isn’t just financial—it’s multidimensional, affecting operations, trust, and compliance.
Legal and regulatory consequences: Depending on jurisdiction, companies can face hefty penalties for data exposure.
Customer loss: Studies show over 60% of users abandon a brand post-breach.
Brand erosion: News of a breach often dominates headlines and search engine results, haunting companies for years.
For small businesses, a successful formjacking attack can be fatal. For large enterprises, it may translate to millions in fines, lawsuits, and cleanup costs.
Beyond monetary implications, customers impacted by formjacking often face payment card data fraud, identity theft, and emotional distress—making your company liable for long-term support and remediation.
The bottom line? Formjacking attacks may take seconds to execute, but the damage can last for years.
Why Fidelis Deception Is the Right Choice
Fidelis Deception is not just about setting traps—it’s about active defense that blends into your environment.
With Fidelis Deception, you can:
Deploy decoy forms and assets that mirror your real infrastructure
Instantly identify formjacking attempts when attackers engage with bait forms
Collect telemetry and behavioral insights to respond in real time
By implementing deception at the endpoint, server, and application levels, you can turn your environment into a minefield for attackers.
Ready to stop formjacking attack before it starts?
Discover how Fidelis Deception can trap attackers before they breach your real assets.
Deploy decoy forms and lures
Detect stealthy data exfiltration
Turn insights into active defense
Conclusion
Formjacking is growing, stealthy, and dangerous. But it’s also preventable—with the right tools, strategy, and awareness.
By understanding how formjacking works, continuously monitoring your site, and embracing proactive technologies like deception, you can ensure your business doesn’t fall victim to this silent threat.
Start by evaluating your security posture today—and let Fidelis help you stay one step ahead.
The post What Is Formjacking and How Can You Detect It? appeared first on Fidelis Security.
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