How should security teams extend SaaS security coverage to custom and lesser known applications?

How SaaS Coverage Breaks Down Around Small and Custom Apps

The gap usually appears because teams scope “SaaS security” around the largest, most visible vendors and then let smaller applications fall into a separate review path. That creates uneven control coverage, even when the smaller app still stores data, issues tokens, or connects to sensitive workflows. A better model is to classify applications by data access and integration risk, not by brand recognition.

That matters because custom apps often inherit the same failure modes as mainstream SaaS: weak authorization, overbroad access, stale accounts, and unreviewed integrations. The difference is not that the risk is unique, it is that the control baseline is often missing or inconsistent.

One useful reference point is the pattern seen in incidents such as Salesloft OAuth token breach and Dropbox Sign breach, where access was extended through tokens or service accounts rather than through the most obvious user-facing controls. Those cases show why “small app” does not mean “small blast radius” once the app is wired into a larger SaaS ecosystem.

What Needs to Be Extended Across the Long Tail

Security teams should extend the same core checks they already apply to major SaaS platforms: inventory, ownership, authentication method, integration scope, privilege level, data classification, logging coverage, and offboarding process. The practical test is whether the application can create, read, move, or expose business data, or whether it can invoke another system on behalf of a user or workflow.

For custom applications, the main challenge is often not discovery but normalization. If the app cannot be onboarded into central visibility, teams should still require a minimum control profile that covers configuration review, access review, and token or API key management. The point is to avoid separate standards for “official” SaaS and everything else.

That approach aligns with broader SaaS governance patterns captured in the CSA Cloud Controls Matrix, especially around IAM, auditability, and data protection. It also fits the control logic in NIST SP 800-53 Rev 5 Security and Privacy Controls, where access control, configuration management, and audit trails are expected to apply across systems, not just major providers.

Where teams need a more SaaS-specific lens, the most relevant internal guidance is the Ultimate Guide to NHIs, because the operational problems in custom SaaS frequently show up through secrets, tokens, service accounts, and third-party integrations rather than through interactive users alone.

Practitioner Guidance

What to prioritise: Put custom and niche SaaS into the same discovery and review pipeline as the mainstream stack, then rank them by data sensitivity and integration privilege. A low-profile app that can call production APIs is more important than a high-visibility app with no downstream reach.

What to verify: Confirm that every app has an owner, an access model, a revocation path, and a logging source you can actually query. If you cannot answer who approved it, what it can reach, and how access is removed, treat it as ungoverned until proven otherwise.

Common mistake: Teams often rely on SaaS catalogs or procurement lists and miss shadow or departmental tools that were built to solve a local problem. Those apps become persistent exceptions unless you force them into the same controls for data handling, privilege review, and integration monitoring.

Practitioner takeaway: Coverage should follow trust and exposure, not vendor size, because the security failure in a small application is usually that it was allowed to stay “small” in governance even after it became part of a larger data path.

Related resources from NHI Mgmt Group

• How should security teams extend Zero Trust coverage to disconnected SaaS apps and shadow IT?
• How should security teams close SaaS security coverage gaps across thousands of applications and integrations?
• How should security teams automate access grants and revocations across cloud, SaaS, and custom applications without creating provisioning drift?
• How should security teams extend SSO beyond SaaS without leaving legacy and on-prem applications exposed?