Custom apps are software applications built for a specific organisation or use case rather than bought as a standard off-the-shelf product. They are often developed in-house or by a contractor and may expose APIs, service accounts, tokens, or certificates that need ownership, access control, and lifecycle management.
What Custom Apps Usually Need to Govern
Custom apps are rarely just code. They usually include owned APIs, backend services, configuration, deployment pipelines, and identity-bearing material such as service accounts, tokens, and certificates that need clear ownership and lifecycle control.
Because the application is built for one organisation or use case, the security posture depends less on a generic product baseline and more on whether the organisation has defined who owns access, who approves changes, and who can revoke trust when the app or its dependencies change.
Why Custom Apps Create Distinct Security Exposure
Custom apps tend to inherit risk from the way they are assembled, not just from the code itself. A bespoke integration may expose internal APIs, trust third-party components, or embed secrets in places that are hard to inventory, which makes the attack surface more variable than in packaged software.
This is why app-specific access paths matter. The Shopify App Tokens Security Guide is a useful example of how token scope, storage, rotation, and logging become security issues as soon as an app needs persistent access to external systems. For broader access governance, Entra ID Entitlement Management and Access Packages Guide shows the same ownership problem from the access-control side.
Access, Secrets, and Lifecycle Boundaries
The hardest part of custom app security is often not the feature set, but the boundary around credentials and permissions. Service accounts, API keys, refresh tokens, webhook secrets, and certificates can outlive the code that created them, and that creates drift between what the application does and what its access still allows.
That drift matters because custom apps are often maintained by different teams over time. Without explicit lifecycle ownership, access may remain active after a project ends, a contractor leaves, or an integration is replaced. In practice, the app’s security depends on whether each secret and credential has a known owner, an expiry or rotation rule, and a revocation path.
Configuration and Integration Failures to Watch
Custom applications fail in predictable ways when they are deployed with weak defaults, copied environments, broad permissions, or unclear trust boundaries between modules and integrations. The most common issue is that a custom app becomes “special” operationally, but ordinary in governance, so no one maintains it with the same rigour as a core platform.
For readers who need a control baseline, the OWASP Top 10 and the OWASP API Security Top 10 are strong references for the application and API failure modes most likely to affect custom software. If the app depends on machine-to-machine trust, the NIST SP 800-53 Rev 5 Security and Privacy Controls controls for access control, authentication, auditing, and configuration management provide a practical policy baseline.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 addresses the attack surface, OWASP ASVS and NIST SP 800-53 Rev 5 set the technical controls, and ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP ASVS | V4 — API and Web Service | Custom apps often expose APIs that need verification of access control and service security. |
| Recommendation — Verify API authorization, input handling, and service boundaries for each custom application. | ||
| OWASP API Security Top 10 | API1 — Broken Object Level Authorization | Custom apps frequently expose object-level API paths that can be overbroad by design. |
| Recommendation — Test custom app APIs for object-level authorization gaps and enforce per-object access checks. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Custom apps rely on credentials, tokens, and secrets that need lifecycle control and rotation. |
| AC-6 — Least Privilege | Custom apps commonly accumulate excessive permissions across service accounts and integrations. | |
| Recommendation — Manage app secrets and tokens with defined issuance, rotation, revocation, and storage rules. Restrict each custom app credential to the minimum permissions needed for its function. | ||
| ISO/IEC 27001:2022 | A.5.15 — Access control | Custom apps need policy-defined access rights for users, services, and supporting accounts. |
| Recommendation — Define, approve, and review access rights for custom applications under formal access control policy. | ||
Practitioner Guidance
Governance implication: Treat each custom app as an owned security asset, not just a codebase. The app should have a clear business owner, a technical owner, and an explicit inventory of the credentials, APIs, and external dependencies it uses.
What to watch for: The highest-risk signal is usually silent access drift, where the app still has valid credentials or broad permissions even after its original purpose has changed. That is especially important when the app was built by a contractor, integrated quickly, or deployed outside standard platform controls.
Practitioner takeaway: If an organisation cannot answer who can revoke the app’s access, it does not yet have full control of the app.
Related resources from NHI Mgmt Group
- Why do custom applications create more identity governance risk than packaged SaaS apps?
- What do teams get wrong when they rely on custom auth logic for complex apps?
- How should IT teams automate access reviews and lifecycle changes across SaaS and custom apps without relying on manual oversight?
- What do teams get wrong when they build custom organization switching in B2B apps?