Trust boundary
A point where data or execution crosses between contexts with different privileges, ownership, or security assumptions.
- Also called
- trust boundaries
- Defined in
- OWASP Threat Modeling Cheat Sheet
Covered in
Review a code change through its trust boundaries
Turn a pull request into a small set of security claims that can be checked against the surrounding system and tests.
Choose a threat modeling method and turn its findings into tests
Use the four-question frame to scope a design, pick STRIDE, attack trees, LINDDUN or PASTA by the question you need answered, and leave behind threat records and abuse-case tests the team can run.
Consume third-party APIs safely (OWASP API10:2023)
Treat every upstream and third-party API response as untrusted input: validate it against a schema, set connect and read timeouts, cap the response size, refuse to follow redirects blindly, keep TLS verification on, and scope the credentials you hold for each provider.
Review trust boundaries in mobile and native clients
Protect local data and platform interactions while keeping server-side authorization independent of the client’s behavior.
Constrain MCP and multi-agent trust boundaries
Validate each connection and delegated action without treating a token for another service, a tool description, another agent or a state handle as authority.
Worked threat model: a mobile banking app
A complete worked threat model for a mobile banking-style app: the data-flow diagram and its elements, STRIDE threats on the client, the transport and the backend, and the mitigations mapped to OWASP MASVS v2 controls and current Android and iOS platform APIs.
All 7 pages that cover Trust boundary in the library
Practice: Local project: Secure a real HTTP API · Local project: Enforce retrieval and tool boundaries across crashes · Local project: Keep an iOS app's storage, links and web bridge in bounds · Local project: Repair an Android app's links, components, network policy and storage