Your API works.Your data can still leak.
We test real API behavior to prove whether tenant isolation, object access, and authorization still hold when actors, roles, and object ownership stop lining up.
Initial findings within 48 hours with reproducible cross-tenant leak scenarios.
Primary audit path: request-level proof first, remediation guidance second.
Healthy telemetry can still hide a tenant leak.
Actor
Valid session
Check
Ownership missing
Impact
Cross-tenant data exposure
This audit is built for silent failures where availability stays green while the wrong tenant still receives the data.
What you get from the audit
The output is architecture-first and proof-based: where the leak happens, why it happens, and what has to change for the tenant boundary to hold.
Exact leak paths
We show the endpoint, actor mismatch, and tenant boundary that fails under a real request.
No checklist-only findings.
Reproducible proof
Each finding includes a repeatable scenario your team can replay during remediation and retest.
Root cause clarity
We tie failures back to object access, EF Core scope drift, cache keys, or async context loss.
Fix guidance
You get code-level remediation direction, not vague recommendations about security posture.
Where SaaS authorization usually breaks
Cross-tenant exposure rarely looks dramatic. The request succeeds, the session is valid, and the payload still belongs to the wrong tenant.
- Object IDs are trusted without ownership validation.
- EF Core includes and joins drift outside tenant scope.
- Cache keys reuse valid payloads across tenants.
- Background jobs and exports lose tenant context after the request ends.
Why telemetry misses it
Monitoring tracks availability and errors. It does not prove that the returned object belongs to the right tenant.
Why teams find it late
The issue usually appears only when actor, role, and object ownership stop lining up under a real request permutation.
What we test directly
API authorization
Endpoint behavior, object access, and role checks under controlled actor mismatch.
EF Core query paths
Includes, joins, and repository lookups that bypass tenant predicates quietly.
Cache isolation
Shared keys and response reuse that replay valid data to the wrong tenant.
Async workflows
Jobs, exports, and workers that stop carrying tenant identity outside request scope.
Observed request
GET /api/orders/123
Actor context
Tenant A session
Leak result
Tenant B record returned with 200 OK
How the audit runs
We test the tenant boundary the same way it fails in production: through real request flows, controlled mismatch scenarios, and repeatable response analysis.
Boundary review
We map tenant context, actor roles, object ownership paths, and high-risk API surfaces.
Request mutation
We vary tenant, role, and object combinations to expose authorization drift under normal traffic patterns.
Response diffing
We compare status, payload shape, and returned fields across controlled actors and tenants.
Root cause isolation
We trace the break to query logic, ownership checks, cache scope, or worker context propagation.
Fix planning
We define the remediation path for controllers, services, EF Core queries, and tenant context handling.
Validation retest
We replay the same exploit paths after fixes to confirm the tenant boundary now holds.
When this audit is worth doing
The strongest trigger is uncertainty. If you cannot explain how tenant scope is enforced across API, data access, cache, and async work, the boundary is already weak.
Enterprise review approaching
You need proof that tenant isolation holds before procurement or customer security review.
API surface has grown
New endpoints, exports, and integrations add object access paths that drift out of scope quietly.
Authorization logic is fragmented
Ownership checks are spread across controllers, services, queries, and workers, so confidence drops fast.
Sensitive tenant data is in scope
Financial, healthcare, legal, or operational records make silent leaks expensive the moment they externalize.
Audit scope based on API risk and tenant-boundary depth
Start with proof on a critical API surface or expand into a deeper audit when the findings point to broader architecture risk.
For a narrow, high-risk API surface
Focused authorization review of the endpoints and workflows most likely to leak across tenants.
Best when you need fast proof on a specific product area before review or release.
Project Investment
From EUR 1,500
Initial findings within 48 hours with reproducible leak scenarios and clear remediation direction.
- Critical endpoint review
- Actor and object mismatch testing
- Cross-tenant response comparison
- Short findings summary
- Prioritized fix guidance
- Retest scope defined for follow-up
Recommended for live multi-tenant products
Deeper audit across API authorization, EF Core data access, cache scope, and async context propagation.
Best when you need a serious review of the tenant boundary, not only a spot check of a few endpoints.
Project Investment
From EUR 2,500
The main audit path for teams that need architectural clarity and proof before issues reach customers.
- Everything in Audit Sprint
- EF Core query-path review
- Cache and worker isolation checks
- Root cause explanation per finding
- Remediation planning support
- Validation retest after fixes
For teams already planning remediation
Audit coverage plus a tighter remediation loop when findings point to deeper tenant-boundary architecture work.
Best when you expect the fixes to touch repository patterns, middleware, or broader SaaS architecture.
Project Investment
Custom scope
Use this when the audit needs to flow directly into implementation support and retesting.
- Everything in Core Audit
- Fix review across implementation paths
- Expanded validation on resolved issues
- Architecture-level remediation guidance
- Development handoff support
- Bridge into secure SaaS implementation work
When the findings point to architecture, the next step is implementation.
Some audits end with targeted fixes. Others show that tenant isolation, repository patterns, authorization flow, or async context propagation need broader system work.
That is where our SaaS development work starts: rebuilding the boundary so the same exploit path no longer exists.
Need the fixes implemented?
Review how we design multi-tenant SaaS systems with tenant isolation, RBAC, billing logic, and secure APIs.
Who this is for
This audit is built for multi-tenant SaaS teams that need proof before customer exposure, enterprise review, or remediation planning forces the issue.
Founders selling into larger accounts
You need tenant-boundary proof before enterprise buyers ask harder questions.
Teams running multi-tenant APIs
Your risk sits in request handling, object access, and authorization enforcement, not only in infrastructure.
Products with EF Core and async workflows
Joins, includes, exports, and jobs are common places where tenant scope disappears.
Engineering teams planning fixes
You want to know whether the problem is a local authorization bug or an architectural boundary issue.
Questions teams ask before a SaaS security audit
Short answers on scope, runtime testing, source access, and how we validate tenant boundaries in real APIs.
What is a SaaS security audit?
It is a focused review of tenant isolation, authorization, and data access paths in a multi-tenant application. The goal is to find broken access control, BOLA, and cross-tenant exposure at the application layer.
What is the difference between SaaS and API security audit?
A SaaS security audit looks at the full multi-tenant application, while an API security audit focuses on endpoint behavior, object access, and authorization logic. In practice, the API layer usually carries most of the risk.
Can an API be vulnerable even if it returns 200 OK?
Yes. Many authorization failures return 200 OK while exposing data from another tenant. Response success only means the request executed, not that access control was correct.
Do you test multi-tenant systems specifically?
Yes. We test tenant context propagation, tenant-scoped queries, cache boundaries, and object access across multiple tenants. Multi-tenant security is the main focus of the audit.
Do you detect broken access control (BOLA)?
Yes. We test object IDs, ownership checks, role transitions, and request mutation scenarios to identify broken access control and BOLA in APIs and workflows.
Do you need source code?
Not always. We can start from runtime behavior and API testing. Source access increases depth and speeds remediation, especially for EF Core, middleware, and background jobs.
Can caching or background jobs leak tenant data?
Yes. Shared cache keys, reused responses, and worker jobs that lose tenant context can leak data even when the main API path looks correct. We test those flows directly.
How long does audit take?
Initial findings are typically delivered within 48 hours. Full depth depends on API surface, tenant model complexity, and system access.
Can you detect issues without logs?
Yes. Most cross tenant authorization failures do not generate clear errors. We detect them by controlled actor and object testing with response level analysis.
Find the leak path before your customer does.
Primary next step: request the audit. If the findings lead into deeper tenant-boundary remediation, the development path is ready after that.