Defines assets, threats, trust boundaries, required controls, secure defaults, and implementation guidance for security headers. It fixes adoption boundaries and observable failure evidence while keeping environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Security headers, adopt a threat model and server-enforced control at the protected boundary. Enforce the control on the trusted server side, default to denial, and define threat assumptions, abuse limits, evidence, and recovery. This security block focuses specifically on control specification. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Security headers actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes required for the control specification focus of this security block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Name assets, actors, trust boundaries, attacker capabilities, abuse cases, assumptions, and residual risk before selecting controls.
- Fail closed for protected operations when identity, policy, integrity, freshness, or resource scope cannot be established.
- Bound work and attempts per actor, credential, tenant, resource, and infrastructure capacity without trusting client-supplied identity alone.
- Keep secrets and sensitive payloads out of logs while retaining control version, correlation, decision, and safe reason as evidence.
- Treat all client, callback, file, model, and telemetry fields as untrusted until authenticated and validated for the intended action.
- Require a second independent safeguard for high-impact paths where one parser, credential, or provider compromise would otherwise be decisive.
- Define header policy by route and content type for transport enforcement, content execution, framing, MIME interpretation, referrer disclosure, browser capabilities, and cache behavior.
- Roll restrictive policies through report and enforcement evidence where applicable, minimize exceptions, test redirects and error pages, and verify that CDN, proxy, and application layers do not overwrite one another.
- For the control specification variant, enforce this declared boundary: defines assets, threats, trust boundaries, required controls, secure defaults, and implementation guidance for security headers.
Implementation guidance
- Threat-model normal, replay, enumeration, cross-tenant, automation, and degraded-dependency paths before implementation review.
- Model Security headers inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Security headers contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- Control degradation preserves the protected boundary, raises an owned incident signal, and never grants access solely to maintain availability.
- Invalid or contradictory Security headers state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Use paired allow and deny cases at every trust boundary and confirm that loss of the control dependency fails closed.
- Monitor Security headers success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.