Healthcare teams should treat security testing as part of deal due diligence, not a post-close cleanup activity. The goal is to find exposed systems, weak authentication, missing controls, and compliance gaps before attackers do. Testing should cover both environments being combined, because one vulnerable asset can create a path into the wider attack surface and increase the risk of patient data exposure, operational disruption, and regulatory penalties.
Testing Before Close, Not After Integration
In a healthcare merger or acquisition, security testing should be treated as a transaction control, not a post-close hardening task. The practical question is whether each environment can be safely connected, trusted, and supported without importing hidden exposure into clinical systems, revenue-cycle platforms, or patient data workflows.
That means testing the target and acquiring environments separately first, then testing the combined trust boundary where systems, users, APIs, and integrations will meet. The review should be broad enough to surface exposed services, authentication weaknesses, missing logging, unsupported systems, and high-risk configurations before they become shared problems.
For web-facing systems and APIs, a structured approach such as the OWASP Web Security Testing Guide helps teams move beyond ad hoc scans and verify controls in a repeatable way. For configuration hardening across servers, databases, and network devices, CIS Benchmarks provide a practical baseline for identifying inherited misconfiguration before systems are merged.
What to Test Across Both Sides of the Deal
Healthcare teams should focus on the control failures that most often turn an acquisition into an incident: weak authentication, excessive access, exposed secrets, unsupported software, and poor segregation between environments. A single weakly protected asset can become a bridge into the broader estate, especially where shared identity systems, VPN access, third-party connections, or legacy interfaces already exist.
Testing should also confirm whether the target environment can continue operating safely during integration. That includes backup and recovery assumptions, segmentation between clinical and non-clinical systems, and whether monitoring actually covers the assets that will be inherited. If those controls are incomplete, the acquisition can expand operational blast radius even when no active attacker is present.
For identity and secret handling, the OWASP Non-Human Identity Top 10 is useful because merger activity often exposes service accounts, API keys, and other machine credentials that are easy to overlook during due diligence. Where web services or APIs are being integrated, the OWASP API Security Top 10 helps teams check authorisation boundaries that may not be obvious from infrastructure reviews alone.
Risk and Threat Considerations
Merger and acquisition testing is high value because attackers often benefit from temporary confusion, duplicated controls, and incomplete asset visibility. Healthcare adds extra consequence: exposure can affect patient records, clinical availability, and regulatory standing at the same time, so an inherited weakness can become both a security and business continuity issue.
Failure mechanism: Security testing that happens only after close misses the transition window when trust is being expanded, credentials are being shared, and integrations are being turned on. In that gap, exposed services, weak authentication, or stale accounts can persist long enough to create lateral movement paths or unauthorized access to sensitive systems.
Impact: The likely result is broader attack surface, delayed containment, and avoidable exposure of protected health information. In a regulated environment, that can also mean reporting obligations, contractual issues, and remediation costs that are far harder to absorb after the systems are operationally intertwined.
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 |
|---|---|---|
| CIS Controls v8 | CIS 4 — Secure Configuration of Enterprise Assets and Software | M&A testing must expose inherited misconfiguration and hardening gaps. |
| CIS 6 — Access Control Management | The question centers on finding weak authentication and excessive access before close. | |
| CIS 8 — Audit Log Management | Testing should confirm inherited systems are monitored before they become shared. | |
| Recommendation — Validate inherited systems against secure baselines before allowing integration. Review and remove inherited access paths before merging environments. Verify logging and alerting coverage across both estates before cutover. | ||
| NIST CSF 2.0 | PR.AC — Access Control | Healthcare deal testing must validate who can access newly connected systems. |
| PR.IP — Information Protection Processes and Procedures | Due diligence should test whether protection processes survive integration. | |
| DE.CM — Security Continuous Monitoring | Merger testing should ensure visibility exists before systems are operated together. | |
| Recommendation — Assess and tighten access control before trust relationships are expanded. Check inherited protection procedures before combining environments. Confirm monitoring coverage for both estates and the new shared boundary. | ||
| OWASP Non-Human Identity Top 10 | NHI-01 — Secrets and Credential Sprawl | M&A reviews often uncover exposed secrets and service credentials. |
| NHI-03 — Overprivileged Non-Human Identities | Inherited service accounts can create excessive access during integration. | |
| NHI-06 — Third-Party and Supply-Chain Exposure | Acquisitions often inherit external dependencies and shared trust paths. | |
| Recommendation — Inventory and eliminate exposed secrets before integration. Reduce inherited machine privileges before opening cross-environment access. Test third-party connections and shared trust relationships before merger. | ||
| OWASP Agentic AI Top 10 | A7 — Identity and Access Abuse | Where automation and agents are present, merger testing must check abused access paths. |
| Recommendation — Verify autonomous and automated access cannot exceed intended authority. | ||
Practitioner Guidance
What to prioritise: Begin with the highest-blast-radius assets, such as identity systems, externally reachable services, EHR-adjacent integrations, and anything that can authenticate into production. If those are weak, the acquisition should be treated as a risk containment exercise before it becomes a migration project.
What to verify: Confirm that test results cover both estates and the new trust paths between them, not just point-in-time vulnerability scans. The evidence that matters is whether teams can show exposed assets, privileged accounts, secrets storage, and logging gaps were reviewed before connectivity expanded.
Practitioner takeaway: The safest deal posture is to assume every new connection increases trust until testing proves otherwise; if you cannot explain the exposure and control state of both environments, you do not yet have enough assurance to integrate them.
Related resources from NHI Mgmt Group
- How should security teams assess identity risk during an acquisition or merger?
- How should healthcare security teams handle identity visibility during post-merger domain consolidation?
- How should security teams use DLP during a merger or acquisition to reduce data leakage risk?
- What do security teams get wrong about PAM during post-merger integration?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 19, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
