What Is The Blind Spot In Your Attack Surface?

The growing attack surface

External connectivity has become inseparable from modern operations. From cloud service providers and SaaS platforms to open-source libraries and CDNs, organizations are increasingly dependent on infrastructure they do not own. These connections support agility but also introduce a growing attack surface that is often invisible to internal systems.

When organizations fail to monitor third-party exposures with the same precision they apply to internal assets, risk accumulates unchecked. A single integration or vendor platform can become an unmonitored conduit for exploitation. Breaches originating from third-party systems are no longer exceptional. They are routine.

Understanding and managing this risk requires extending visibility beyond the traditional security perimeter. Attack Surface Management (ASM), when built to observe external infrastructure continuously, provides a direct path toward addressing these blind spots. Without it, organizations operate with assumptions. With it, they operate with evidence.

This blog ties into the release of our brand new eBook “ASM in the Age of CTEM.” To learn more about building a mature ASM program download the eBook.

The Attack Surface Is No Longer Contained

Many security programs still treat third-party services as operational dependencies rather than attack surface components. This is a costly mistake. Whether it is a SaaS billing tool, a customer analytics platform, or an integration with a logistics provider, the moment an external system receives sensitive data or is granted access to core functions, it becomes a potential point of compromise.

The architecture of modern business systems creates lateral trust across organizational boundaries. Vendors are assigned credentials, APIs are granted permissions, and embedded components load external code. These are not marginal risks; they are embedded into core workflows.

The distinction between internal and external systems has collapsed. Security teams can no longer afford to monitor only what they control. The full attack surface includes every service, connection, and dependency that touches customer data, application logic, or administrative functionality.

Supply Chain Attacks Are Now Standard

Targeting suppliers, vendors, and service providers has become a reliable and repeatable strategy for attackers. Compromising a single vendor can yield access to hundreds of downstream organizations. Whether the goal is data theft, extortion, or lateral movement, attackers understand the reach and reuse of third-party infrastructure.

Examples abound. Compromised SDKs inject malicious code into thousands of mobile apps. Vulnerabilities in popular libraries result in widespread data leaks. Misconfigured APIs become entry points for credential harvesting. The methods differ, but the principle is the same: the easiest way into a hardened environment is through a softer target that is already trusted.

Security teams often lack the telemetry needed to detect these incidents. Internal controls provide no early warning when a breach begins with a third-party script or a vendor-maintained API. Monitoring fails, not because of a lack of tooling, but because the tooling was scoped incorrectly.

Trust Without Visibility: Vendor APIs and Plugins

Vendor APIs are necessary for automation, reporting, and workflow integration. They simplify business processes by enabling direct access to external systems. But with convenience comes exposure.

APIs are often provisioned with persistent credentials and broad permissions. Token rotation may be inconsistent, and audit trails may be insufficient. In many cases, these APIs are embedded deep in codebases and forgotten until they break.

Plugins and integrations introduce similar challenges. They extend functionality by pulling external code directly into production environments. This code often executes with the same privileges as internal applications but is maintained by third parties with different development standards and security practices.

Once an API or plugin is connected, it is granted a level of implicit trust. The consequences can be significant if that trust is abused through compromise, misconfiguration, or intentional misuse. Yet most organizations do not apply the same exposure monitoring to vendor systems as they do to their own.

JavaScript Dependencies and CDN Risks

Few organizations control every line of code that runs in their customer-facing environments. JavaScript dependencies are imported from external sources and often loaded directly from public CDNs. These scripts are subject to change at any time. A well-timed update from a compromised CDN can affect thousands of websites simultaneously.

Even internally hosted copies of third-party scripts can introduce vulnerabilities. Libraries may be outdated, unpatched, or contain insecure logic that was never audited. Because these components are often treated as static assets, they fall outside the scope of dynamic vulnerability scanning or behavioral analysis.

Supply chain compromises of JavaScript libraries are difficult to detect and easy to exploit. A single modified script can exfiltrate session tokens, intercept credentials, or inject malicious UI elements. Because the attack vector originates outside of core infrastructure, detection depends on visibility that most security teams lack.

Ownership Gaps and Diffused Accountability

Managing third-party risk is not just a technical challenge. It is also an operational one. In many organizations, no single team owns vendor security outcomes. Procurement may vet initial contracts. IT may manage onboarding. Security may perform limited point-in-time reviews. But ongoing oversight is often absent.

This fragmented ownership model results in long-lived, high-trust connections with little or no monitoring. APIs continue to operate years after contracts expire. Access tokens remain active for systems that are no longer in use. Exposed endpoints persist because no team is accountable for their remediation.

ASM provides a mechanism for centralizing this responsibility. By treating vendor infrastructure as part of the external attack surface, security teams gain visibility into the assets and connections that influence their risk posture, even if they are not the system owners.

Extending ASM to Monitor Vendors

Traditional asset management assumes ownership. ASM assumes exposure. That distinction is essential when managing third-party risk.

Effective ASM platforms discover and track infrastructure across domains, not just within them. They correlate DNS, certificates, behaviors, and relationships to build an accurate view of what is truly exposed, whether it belongs to the organization or to a trusted partner.

When configured to monitor third-party domains, ASM can alert on new subdomains, detect changes in technology stacks, identify exposed APIs, and monitor for the presence of suspicious scripts. It can also detect misconfigurations that place vendor systems at risk, such as open administrative panels, unprotected storage buckets, or known-vulnerable libraries.

This visibility transforms third-party risk management from a static compliance process into a continuous monitoring capability. It allows security teams to act on real-time data rather than relying on periodic assessments or vendor attestations.

Aligning ASM with CTEM

Continuous Threat Exposure Management (CTEM) depends on visibility. Without accurate, real-time data about what is exposed, CTEM workflows cannot prioritize or validate risk. This limitation is amplified when exposure originates from third-party systems.

Integrating ASM with CTEM extends the scope of exposure management beyond owned infrastructure. Vendor domains and services are included in scoping. Their exposures are validated using the same methods as internal systems. With the appropriate context and urgency, remediation can be routed through procurement, legal, or business owners.

CTEM becomes more effective when it incorporates external attack surface data. Threat intelligence, vulnerability validation, and prioritization workflows all benefit from a broader view of where and how risk manifests. Vendor systems are part of that view.

Five Practical Steps for Managing Vendor-Originated Exposure

1: Maintain a Live Inventory of Third-Party Domains and APIs

Use ASM to discover and track domains, APIs, and cloud services connected to your environment. Include CDNs, integration partners, and authentication providers.

2: Monitor for Changes in Vendor-Facing Assets

Configure alerting for DNS changes, new subdomains, or shifts in technology usage. Unexpected changes can indicate compromise or risky updates.

3: Tag and Prioritize Based on Business Impact

Not all vendors introduce equal risk. Use tagging to map exposure severity to business functions. Prioritize validation and remediation based on data sensitivity and operational dependency.

4: Route Verified Exposure to the Right Teams

Ownership may reside outside of security. Use ASM metadata and integration points to assign remediation tasks to procurement, legal, or operational owners.

5: Audit and Refresh Vendor Access on a Defined Schedule

Use ASM to support periodic reviews of active vendor integrations. Validate that APIs, credentials, and scripts in use are current, scoped appropriately, and monitored continuously.

The Risk You Don’t Own Still Belongs to You

Responsibility does not end at the contract boundary. Customers, regulators, and attackers make no distinction between internal and third-party exposures. If a compromise occurs through a vendor system, the organization bears the consequences.

Security programs must reflect this reality. Visibility must extend beyond the infrastructure you manage to include the services, scripts, and connections you rely on. ASM provides that visibility, and CTEM makes it actionable.

Together, they enable a transition from reactive incident response to proactive exposure reduction. That shift is essential for managing modern risk, especially when it originates from someone else’s infrastructure.

You can’t fix what you can’t see, and that includes your vendors.