by Source Defense
Most security teams believe they have a reasonable understanding of the third-party scripts running on their websites. In reality, very few organizations have a complete or accurate picture. What they are facing instead is script sprawl – a rapidly expanding, constantly shifting web of third-party code that is nearly impossible to govern manually.
Script sprawl is not the result of negligence. It is the natural outcome of how modern websites are built and operated.
Over time, organizations add scripts to support analytics, advertising, personalization, customer support, experimentation, fraud detection, and performance monitoring. These tools are often deployed by different teams, through different systems, with different priorities. Once added, scripts rarely disappear. They accumulate. In fact, Source Defense’s first of its kind research in collaboration with Verizon for the 2024 PSR found an exponential increase in the use of third-party scripts, increasing by over 50% in a two-year period of time.
As if this wasn’t enough, the real problem begins when scripts start loading other scripts.
The Hidden Complexity of Script Dependencies
What looks like a single script in a tag manager often turns out to be the first link in a long chain. At runtime, that script may dynamically load additional libraries, vendor services, or partner integrations – many of which were never reviewed or approved.
This creates a layered execution model where:
- Scripts load conditionally based on user behavior
- Dependencies change without notice
- New data flows appear without configuration changes
- Behavior evolves independently of the site’s release cycle
From a governance perspective, this means the environment is changing constantly, even when no one touches the website.
Manual inventories quickly become obsolete. Spreadsheets fall out of date. Documentation drifts from reality. Security teams lose confidence in what they actually control.
Why Traditional Governance Models Break Down
Manual governance assumes a stable environment where changes are intentional and visible. Script sprawl violates both assumptions.
Marketing teams deploy new tools without security involvement. Vendors push updates automatically. A/B testing platforms change execution paths dynamically. Even minor CMS changes can affect how scripts load and interact.
Security teams are left reacting instead of governing.
When an incident occurs – data leakage, compliance violation, or eSkimming – organizations scramble to understand which scripts were active at the time and what they were doing. In many cases, that information simply doesn’t exist.
The Risk Multiplier Effect
Script sprawl doesn’t just increase complexity; it multiplies risk. Each additional script expands the attack surface and introduces new opportunities for misuse, compromise, or accidental data exposure.
The more scripts run on a page, the harder it becomes to enforce least privilege. Sensitive data intended for one function becomes accessible to many. Without runtime controls, organizations rely entirely on trust – trust that vendors behave responsibly, update safely, and never get compromised.
History shows that trust alone is not enough.
Moving Beyond Manual Control
The solution is not better spreadsheets or more frequent reviews. Script sprawl is a systemic problem that requires automated visibility and enforcement at runtime.
Organizations need to understand not just which scripts exist, but how they behave across all pages and user journeys. Without that insight, governance becomes aspirational rather than operational.
Script sprawl isn’t slowing down. The only viable response is to govern scripts the same way we govern endpoints: continuously, automatically, and based on behavior.
Take Control of Script Sprawl
If you cannot reliably inventory every script and dependency, you cannot govern them. Source Defense gives security and compliance teams full visibility into what’s running on every page, plus behavior-based controls that stop eSkimming and data leakage at the point of input.
With Source Defense, you can:
- Automatically inventory third-party scripts, including fourth-party dependencies
- See what scripts are doing in the browser, not just where they load from
- Detect and block suspicious behavior before data leaves the page
- Support PCI DSS 4.0.1 requirements 6.4.3 and 11.6.1 with push-button evidence
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.