by Source Defense
Why the Browser Has Become the Weakest Link and How to Reinforce It
The VikingCloud 2025 Cyber Threat Landscape Report paints a clear picture: cybercriminals are moving closer to the customer. With traditional defenses strengthening around servers and networks, attackers have pivoted to the browser — where most digital transactions and personal data exchanges begin.
The new frontier: client-side attacks
VikingCloud’s research underscores a sharp rise in client-side compromises—attacks that hijack scripts, forms, and other front-end components to steal sensitive data at the point of entry. Browser-based threats such as eSkimming, formjacking, and malicious JavaScript injections have become common entry points for fraud and data theft.
Modern websites rely on dozens, sometimes hundreds, of third- and fourth-party scripts from analytics, chatbots, ad networks, and social media integrations. Each one extends functionality but also increases exposure. According to VikingCloud, this “digital supply chain” is now a primary attack vector for cybercriminals exploiting gaps in visibility and control.
The expanding threat economy
The report highlights that JavaScript-based attacks have surged as the preferred method for harvesting payment data and personally identifiable information (PII). These attacks are inexpensive to deploy, often go undetected for months, and are easily resold or repurposed through underground markets.
Cybercriminals are no longer relying solely on complex server intrusions — instead, they compromise browser sessions to exfiltrate data directly from online forms. This shift has transformed once-harmless website components into powerful tools for credential theft and fraud.
Compliance and accountability pressures are rising
The VikingCloud report also echoes growing regulatory and compliance expectations. With PCI DSS 4.0.1 fully enforced, organizations are required to monitor, inventory, and justify every script that runs in the browser during payment processes. Yet many still rely on traditional Content Security Policy (CSP) or Subresource Integrity (SRI) methods, which VikingCloud identifies as too static to keep pace with today’s dynamic web ecosystems.
CSP and SRI can limit certain attacks, but they cannot monitor real-time behavior or adapt to evolving script changes. As a result, organizations struggle to meet the intent of PCI DSS — to prevent and detect unauthorized script activity.
Why browser visibility must become a core control
VikingCloud’s 2025 data reveals an uncomfortable truth: most organizations lack visibility into what’s happening inside their customers’ browsers. Without continuous monitoring, attackers can silently modify or replace legitimate scripts to skim payment data, capture keystrokes, or clone entire web forms.
This lack of visibility is not just a technical gap — it’s a compliance and reputational risk. Failing to detect client-side tampering can lead to data breaches, brand damage, and fines under PCI DSS, GDPR, and CCPA.
Turning the report’s insights into action: Source Defense
The trends in VikingCloud’s report map directly to the gap that Source Defense was created to close.
Source Defense provides real-time, behavior-based protection for the browser — stopping data theft where it happens: at the point of input. The platform isolates and controls all JavaScript running on your site, including third- and fourth-party code, to prevent eSkimming, formjacking, and unauthorized data capture before it occurs.
By deploying a lightweight, two-line integration, organizations gain:
- Full visibility and inventory of every script and its behavior
- Automated prevention of client-side attacks such as Magecart, digital skimming, and keylogging
- Continuous monitoring and alerts aligned with PCI DSS 4.0.1 compliance
- Proactive blocking of malicious script actions without breaking legitimate site functionality
In short, Source Defense operationalizes what the VikingCloud report calls for: moving from passive oversight to active browser defense.
Explore how Source Defense Protect and Source Defense Detect deliver continuous client-side protection and compliance assurance.
Organizations using Source Defense can turn compliance into confidence — protecting customers and meeting PCI mandates through automated visibility, behavioral control, and continuous monitoring.
Key Takeaways for Security and Compliance Leaders
- The browser is now a primary fraud surface. Your JavaScript supply chain is large, dynamic, and often invisible.
- Static defenses alone can’t keep up. Behavior-based, real-time controls are required to prevent data theft at the source.
- PCI DSS 4.0.1 compliance demands both preventive and detective controls in the browser. Source Defense delivers both quickly and efficiently.
See how your site measures up. Request a Demo today and discover how to close the client-side security gap in under 30 days — before attackers or auditors find it first.
PCI DSS 4.0 makes client-side security a priority.
Source Defense delivers a solution for 6.4.3 and 11.6.1 without adding a burden to your security teams.