A single approach leaves gaps because SAST is strongest on source-level issues, while DAST is strongest on runtime vulnerabilities and attack paths visible only in a live environment. If teams rely on one method alone, they can miss flaws that surface later in execution or after deployment. That gap increases the chance of exploitable defects reaching users.
Why one testing method leaves blind spots
A single application security testing approach always reflects a narrow view of the system. Static testing is strongest when issues are present in code paths, insecure patterns, and early design choices, while dynamic testing is strongest when the application is running and behaviour depends on configuration, state, integrations, or authentication flows. The risk is not duplication, it is partial coverage.
That matters because many exploitable defects are only visible in one phase of the lifecycle. A team that relies on only source-level analysis can miss runtime exposure, and a team that relies only on live testing can miss issues that exist in unreachable code, deferred execution paths, or components not exercised during testing. The result is a false sense of assurance.
For a broader testing baseline, practitioners often map this split back to the OWASP ASVS and the OWASP Web Security Testing Guide, because both help teams think in terms of control coverage rather than a single test method.
Where the gaps usually appear in practice
The biggest failure mode is assuming one method can validate the whole security posture. Static analysis does not execute the application, so it can miss issues that emerge only after deployment, such as environment-specific misconfiguration, broken access control in real workflows, or vulnerabilities triggered by a specific sequence of requests. Dynamic testing, by contrast, may miss code that is never reached during a test run or may underrepresent edge cases buried in branches, libraries, or uncommon inputs.
- Source-level testing can miss runtime-only weaknesses such as logic flaws, authentication state issues, or behaviour created by integrations.
- Runtime testing can miss dormant defects, edge-case input handling, and unreachable paths that still become dangerous later.
- Neither approach alone fully captures the security effect of deployment context, data flow, or operational configuration.
That is why strong programmes use complementary methods, then validate the remaining surface with a structured benchmark such as the OWASP Top 10 and the OWASP Web Security Testing Guide. For teams that need broader process maturity, OWASP SAMM is useful for embedding multiple test types into the software delivery lifecycle.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 and OWASP Agentic AI Top 10 address the attack and risk surface, while CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 — Identity and Secret Sprawl | Testing blind spots often let exposed secrets and access paths escape detection. |
| NHI-03 — Secret Rotation and Lifecycle | Runtime and post-deployment gaps can leave exposed credentials undetected for longer. | |
| Recommendation — Scan for secret sprawl and verify controls that prevent hidden credentials from bypassing testing coverage. Verify secret handling across code, build, and runtime so hidden credentials do not evade review. | ||
| CIS Controls v8 | CIS-16 — Application Software Security | AppSec testing depth depends on using complementary verification methods across the SDLC. |
| CIS-17 — Incident Response Management | Missed defects can become incidents after release, so validation must support detection readiness. | |
| Recommendation — Use multiple application security testing methods to cover code, runtime, and deployment weaknesses. Feed testing gaps into response playbooks and monitor for post-release exploitation signals. | ||
| NIST CSF 2.0 | PR.PS — Platform Security | The question is about incomplete security assurance from narrow testing coverage. |
| Recommendation — Apply layered validation to verify that security properties hold in both build and runtime environments. | ||
| OWASP Agentic AI Top 10 | A1 — Agent Goal and Action Control | If applications include autonomous components, single-method testing can miss runtime tool-use failures. |
| Recommendation — Test both static code paths and live action paths when autonomous behaviour is present. | ||
Practitioner Guidance
What to prioritise: Treat testing as layered evidence, not a single gate. If only one method is in place, prioritise the one that covers the largest untested part of the application's lifecycle, then add the complementary method where the risk surface is still under-observed.
What to verify: Confirm that your testing mix covers both code-centric defects and live behavioural defects. If a finding only appears in one environment, check whether the other method can actually observe that class of failure or whether you are depending on it to do work it cannot do.
Common mistake: Teams often over-trust high test volume from one tool and treat it as breadth. A large number of findings from a single approach does not mean the application has been thoroughly assessed if another class of defect remains invisible.
Practitioner takeaway: The goal is not to maximise one test type, but to combine methods so that the blind spots of one are covered by the strengths of another.
Related resources from NHI Mgmt Group
- Why does relying only on simulators create risk in mobile application testing?
- Why does relying on periodic GitHub audits create more risk for application security teams?
- Why does persistent access create more operational risk than a one-time compromise in web application testing?
- Why do mobile apps create different risk conditions than web applications in application security testing?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 20, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
