A new cybersecurity threat is emerging where hackers are injecting malicious scripts into Google Tag Manager (GTM) containers to steal credit card details from e-commerce sites.
This vulnerability is affecting Magento and other e-commerce platforms that rely on GTM for tracking and analytics. Cybercriminals are taking advantage of GTM’s ability to load third-party scripts, turning it into an entry point for skimming credit card information during checkout.
In this article, we will break down:
- How this GTM exploit works
- Why it is dangerous for e-commerce businesses
- How to secure your GTM setup with Two-Factor Authentication (2FA) and other essential measures
How Hackers Are Exploiting Google Tag Manager
Google Tag Manager allows businesses to insert scripts (tags) into their websites without modifying the source code directly. However, this flexibility makes GTM a target for hackers.
The Attack Process
- Hackers gain unauthorized access to a business’s GTM container, either through weak credentials, phishing, or leaked login information.
- They embed stealthy JavaScript skimmers that activate when a customer enters payment details.
- The malicious script records keystrokes or intercepts form submissions, sending the captured data to a remote server controlled by the attacker.
Because GTM scripts execute dynamically, these attacks can be difficult to detect, especially for businesses that do not regularly audit their tag configurations.
How to Secure Your GTM & Prevent Data Theft
If you use Google Tag Manager for tracking and analytics on an e-commerce site, you need strong security practices to prevent unauthorized access and malicious code injections.
Enable Two-Factor Authentication (2FA) on GTM Accounts
One of the easiest and most effective ways to prevent unauthorized access is by enabling Two-Factor Authentication (2FA) on all GTM-related Google accounts.
Instead of just using a password, 2FA requires an additional verification step, such as a mobile app or security key, making it significantly harder for attackers to gain control.
How to Enable 2FA on Google Tag Manager
- Go to Google Account Security Settings
- Scroll down to “2-Step Verification” and click “Get Started”
- Follow the instructions to set up authentication via Google Authenticator, SMS, or a security key
Restrict GTM User Permissions
Not every team member needs full access to your GTM container. Limit user roles based on necessity to reduce exposure risks.
- Administrator: Only for trusted team members who manage GTM settings
- Editor: For users who need to modify tags but not publish them
- Viewer: For users who only need to monitor analytics
Best Practice: Regularly audit user permissions and remove access for former employees or unused accounts.
Monitor & Audit GTM Changes Regularly
To detect suspicious activity, make GTM audits a regular habit.
- Use GTM’s built-in version history to check for unauthorized changes
- Set up alerts in Google Analytics to monitor unusual spikes in activity or script execution
- Manually review custom HTML tags to verify they are not loading scripts from unfamiliar sources
Tip: If you are unsure about a script, scan it using VirusTotal or have a developer inspect its behavior.
Restrict Custom JavaScript in GTM
Hackers use custom HTML tags in GTM to inject malicious code, so only allow trusted scripts to run on your site.
- Whitelist trusted domains for third-party tags
- Avoid unnecessary third-party scripts unless essential
- Limit the use of custom JavaScript tags to prevent unauthorized modifications
Secure Your E-Commerce Platform (Magento, WooCommerce, Shopify, etc.)
- Update your platform and extensions regularly to patch vulnerabilities
- Use a web application firewall (WAF) to block malicious scripts before they execute
- Enable a content security policy (CSP) to restrict which scripts can run on your website
GTM Security is Essential for E-Commerce Businesses
Google Tag Manager is a powerful tool, but if left unsecured, it becomes a backdoor for attackers. By implementing Two-Factor Authentication (2FA), restricting access, and auditing your GTM container regularly, you can prevent credit card skimming attacks and protect your customers’ sensitive data.
If you are running an e-commerce business, securing GTM should be a top priority.
Have you checked your GTM security recently?
