Why do third-party risk programs become inconsistent as vendor ecosystems grow?

Why This Matters for Security Teams

Third-party risk programs become inconsistent because vendor ecosystems expand faster than the review model can scale. A team can manually interpret a questionnaire for ten suppliers, but not for hundreds, especially when product teams, procurement, and security each apply different thresholds. That inconsistency creates uneven approvals, delayed remediation, and hidden exposure across the supply chain.

NHIMG research shows the scale of the problem: 92% of organisations expose NHIs to third parties, which means vendor access is not an edge case but a routine dependency in modern operations from The Ultimate Guide to NHI. The same pattern appears in supply chain incidents such as Reviewdog GitHub Action supply chain attack, where trust in a third-party integration becomes a direct security issue. Current guidance suggests that inconsistent assessment is often less about bad intent and more about fragmented evidence handling, undefined criteria, and reviewer discretion. In practice, many security teams discover the inconsistency only after a vendor has already been onboarded with access that no longer matches the original risk decision.

How It Works in Practice

A consistent third-party program starts by replacing ad hoc judgment with a shared decision model. That means every vendor is evaluated against the same control set, the same evidence requirements, and the same escalation triggers. Instead of asking whether a reviewer feels comfortable, the program asks whether the vendor meets predefined thresholds for data handling, access scope, incident notification, subprocessor controls, and identity hygiene.

Frameworks such as the NIST Cybersecurity Framework 2.0 help structure governance, while the OWASP Non-Human Identity Top 10 is especially useful when the vendor relationship includes API keys, service accounts, or automation tokens. NHIs are a common failure point because third parties often inherit broad access through integrations, and that access is rarely reviewed with the same discipline as human accounts. NHIMG’s Ultimate Guide to NHI notes that 97% of NHIs carry excessive privileges, which makes vendor-connected identities a material control issue, not just a procurement concern.

• Define one rating rubric for all vendors, with clear pass, conditional pass, and fail criteria.
• Require evidence citations for every decision so reviewers can compare like with like.
• Separate inherent risk from residual risk so a high-exposure vendor is not mistaken for a high-quality one.
• Track third-party secrets, API access, and offboarding obligations as part of the same review.
• Reassess vendors on a schedule and after material changes, not only at onboarding.

That approach is reinforced by real-world breach patterns such as the Klue OAuth Supply Chain Breach and the Mastra npm Supply Chain Attack, where trust in software suppliers became trust in their identities and distribution channels. These controls tend to break down when vendor ownership is split across procurement, legal, and security because no single team can maintain a consistent standard of review.

Common Variations and Edge Cases

Tighter vendor controls often increase review time and stakeholder friction, requiring organisations to balance consistency against procurement speed and business urgency. That tradeoff becomes sharper for low-risk SaaS tools, subcontractors, open-source dependencies, and embedded integrations, where the operational value is real but the review depth cannot always be identical.

Best practice is evolving rather than settled in some areas. There is no universal standard for exactly how much evidence a low-risk vendor should provide, but current guidance suggests the answer should be risk-tiered, not reviewer-dependent. High-trust suppliers may justify lighter-touch refreshes, yet they still need consistent minimum controls for access, offboarding, and incident notification. The same is true for vendors that never touch production data but still hold secrets, telemetry tokens, or CI/CD permissions.

Security teams should also account for multi-vendor chains, where one supplier depends on another. That is where the review model most often fragments, because each vendor may look acceptable in isolation while the combined path creates excess exposure. Programs that treat every exception as a documented decision tend to stay consistent longer than programs that allow informal overrides. When vendor ecosystems include automation, secrets distribution, or delegated admin access, consistency erodes fastest because the real risk sits in the identity layer rather than the contract language.

Related resources from NHI Mgmt Group

• Why do third-party risk programs become difficult to scale as vendor volume grows?
• How should security teams reduce risk from dormant SaaS integration credentials in third-party ecosystems?
• Why do third-party access and vendor connections increase compliance risk in regulated financial environments?
• How should security teams implement third-party risk assessments in high-growth vendor ecosystems?