PRD Securability Enhancement (FIASSE/SSEM + ASVS)

Enhance PRD content so each feature has explicit, testable securability requirements aligned to OWASP ASVS and shaped by FIASSE v1.0.4 / SSEM. The goal is to upgrade the requirements artifact before implementation, so delivery teams build securable capabilities by design rather than retrofitting controls later.

This skill is requirements-centric. It does not review or write code. If the user wants code review, redirect to

securability-engineering-review

. If they want code generation, redirect to

securability-engineering

When to Invoke

Trigger this skill when the user asks to:

Strengthen or harden a PRD, spec, user-story set, or product brief with security requirements
Choose an ASVS assurance level (Level 1, 2, or 3) for a product or feature
Map features to ASVS controls or check ASVS coverage of a requirements doc
Find missing security requirements before development starts
Annotate features with SSEM attributes or FIASSE tenets
Add testable security acceptance criteria to existing functional requirements

Adjacent phrasings: "security-review this spec", "what's missing security-wise from this feature list", "add NFRs for security to my PRD", "make these requirements securable".

Inputs

Ask the user for whatever is missing before starting:

The PRD, spec, or feature list (markdown, prose, ticket export, etc.)
System context: user types, deployment model, data sensitivity, integration surfaces
Compliance or risk context, if any (HIPAA, PCI, SOC 2, regulated industry)
Whether they have an ASVS level preference, or want this skill to recommend one

If the artifact is large, parse the features inline; do not require the user to pre-extract them.

Procedure

Step 1 — Parse features

Extract each feature into a normalized record. Capture for each:

Feature ID and title (assign IDs like
```
F-01
```
if absent)
Actor (user role, system, external service)
Data touched and sensitivity class
Trust boundaries crossed (browser↔server, service↔service, server↔storage, internal↔external)
Existing acceptance criteria (verbatim, even if weak)

If the source PRD lumps several capabilities into one bullet, split them so each feature is independently testable.

Step 2 — Choose the ASVS level first

Selecting the level before mapping requirements prevents both under-scoping and over-scoping. Use this rubric:

Level	Use when
1	Internal tooling, prototypes, low-sensitivity data, no regulatory pressure, limited blast radius if compromised
2	Typical production web/API systems with authenticated users, business-critical behavior, customer data, or moderate regulatory exposure (most products land here)
3	High-assurance contexts: payments, health records, government, identity providers, anything where compromise causes severe material impact or where attackers are well-resourced

Default to Level 2 unless evidence pushes lower or higher. Document:

Chosen level
Why lower levels are insufficient (when level > 1)
Any specific features that should escalate above the baseline (e.g., a payments endpoint inside a Level-2 product gets Level-3 treatment)

Step 3 — Map each feature to ASVS

For every feature, use

data/asvs/README.md

(chapter index) and the

when_to_use

frontmatter in

data/asvs/V*.md

to identify applicable chapters. Common mappings:

Auth flows → V2 (Authentication), V3 (Session Management)
Authorization, ownership, multi-tenant scoping → V4 (Access Control)
File upload/download → V5 (File Handling)
Crypto, password storage, tokens → V6 (Cryptography)
Logging, error handling, observability → V7 (Error/Logging)
PII, data at rest/in transit → V8 (Data Protection), V14 (Secure Communication)
Public APIs → V9 (API/Web Services)
Config, secrets, deployment → V10 (Configuration)
Workflow rules, anti-automation → V11 (Business Logic)
Any user/external input → V12 (Input Validation)
Anything rendered or returned to a client → V13 (Output Encoding)
Sensitive data lifecycle → V16 (Sensitive Data)

Filter requirements by the chosen ASVS level. For each requirement, classify coverage:

Covered — the PRD already satisfies the intent
Partial — partly covered; clarify or strengthen acceptance criteria
Missing — requirement absent and must be added
N/A — justified with a one-line rationale

Use the ASVS Coverage Gap Pattern Table below to spot the gaps that PRDs reliably miss.

Step 4 — Add Securability Notes per feature

Write a short paragraph per feature surfacing only the SSEM and FIASSE points that materially shape implementation. Do not enumerate all ten SSEM attributes or all FIASSE tenets — that produces noise.

Useful lenses (mention only when relevant):

Trust-boundary handling and input canonicalization (FIASSE v1.0.4 S4.3, S4.4.1)
Derived Integrity — never trust client-supplied values for server-owned state (FIASSE v1.0.4 S4.4.1.2)
Request Surface Minimization — process only the named values you expect (FIASSE v1.0.4 S4.4.1.1)
Observability: what must be logged or auditable (FIASSE v1.0.4 S3.2.1.4 + Accountability; Transparency S2.5)
Least Astonishment — predictable behavior at trust boundaries and error paths (FIASSE v1.0.4 S2.6)
Resilience or availability drivers (rate limits, timeouts, graceful and secure failure)
Testability or modifiability mandates (e.g., centralizing crypto/auth in a dedicated module)
Dependency stewardship — ongoing relationship with third-party code (FIASSE v1.0.4 S4.6)

Step 5 — Convert into testable acceptance criteria

For each added or strengthened requirement, write at least one acceptance criterion that is:

Behaviorally observable (a test or audit can confirm pass/fail)
Specific about boundary conditions (failure modes, unauthorized actors, malformed input)
Tied to a verifiable artifact (log line, response code, denied action)

Ambiguous "secure" or "robust" language is not acceptable here.

Step 6 — Emit the enhanced PRD artifact

Produce these sections in order, using the exact templates below.

ASVS Coverage Gap Pattern Table

These are the gaps PRDs reliably miss. When you see one of the trigger phrasings on the left, add the named requirements on the right — they are almost always missing in the source artifact.

PRD trigger phrasing (what the feature says)	Almost-always-missing requirements	ASVS section	Tag
"User logs in with email and password"	Account-enumeration parity (same response/timing for valid vs invalid email); password-screen against breached-password list; auth-event audit log; per-account brute-force rate limit	V6.3.8, V2.1, V2.4, V16.3	"Auth surface gaps"
"User resets/forgets password"	Account-enumeration parity on the request endpoint; single-use token; short expiry (≤15 min); token-hash-at-rest; rate-limit per email and per IP; audit log of issuance/redemption	V6.3.8, V6.2, V2.4, V16.3	"Reset flow gaps"
"User uploads a file"	Type allow-list (not deny-list); content-sniffing vs declared type; max size; antivirus/safe-storage path; filename canonicalization; storage outside web root; URL non-guessability	V5.1, V5.2, V12.1	"Upload gaps"
"User can edit their profile" / "update settings"	Allow-listed mutable fields (no `email` / `role` / `is_admin` from request body); ownership check on the resource; audit log of changes; old-vs-new value capture	V4.1, V4.2, V16.2, V16.3	"Mass-assignment gaps"
"Admin can do X" / "role-based access"	Authorization decision logged with grant/deny; centralized authz module (not scattered checks); deny-by-default at boundary; ownership scoping on every record fetch	V4.1, V4.2, V16.2, V16.3	"Authz gap"
"Public API endpoint" / "third-party integration"	Per-key/per-client rate limits; auth for every call (not first-call only); request-id propagation; response field allow-list (no leaking internal fields); contract validation	V2.4, V9.1, V13.1, V16.2	"API gaps"
"Send email/SMS to user"	Templated payload with no user-controlled subject/body injection; rate-limit per recipient and per actor; bounce/abuse-loop handling; opt-out and audit log	V2.4, V12.1, V13.1, V16.3	"Outbound-message gaps"
"Search / filter / list with user-supplied parameters"	Parameter allow-list; ordering/pagination caps; query timeout; result count cap; tenant/owner scoping enforced server-side	V4.1, V12.1, V13.1	"Query-surface gaps"
"Webhook receiver" / "callback URL"	Source verification (signature, mTLS, IP allow-list); replay protection (timestamp + nonce); idempotency key; rate-limit; audit log of received events	V2.4, V2.5, V9.1, V16.3	"Webhook gaps"
"Save user file/document/note"	Owner identifier never client-supplied; size and content caps; rich-text/HTML sanitization on read or write; audit log of writes	V4.1, V5.1, V12.1, V16.3	"Server-owned state gaps (Derived Integrity)"
"Export data" / "download report"	Authorization re-checked on export (not just on UI route); rate-limit; audit log including row count; PII-scrub policy if applicable	V4.1, V7.1.1, V8.1	"Export gaps"
"Background job processes user-submitted data"	Same boundary discipline as the synchronous path (validation, surface minimization, owner scoping); job-level audit log; poison-message handling and DLQ	V11.1, V12.1, V7.1.1	"Async-path boundary gaps"
"Configuration / feature flag / admin setting"	Change requires authenticated actor and audit record; cannot be set via product API without admin role; secret values never echoed back; defaults are safe	V7.1.1, V10.1, V14.2	"Config-surface gaps"
"PII/PHI/financial data" mentioned anywhere	Field-level classification; encryption at rest and in transit; retention/disposal policy; access-log requirement; export/erasure (right-to-be-forgotten) flows	V8.1, V14.1	"Sensitive-data lifecycle gaps"
"Real-time" / "websocket" / "streaming" feature	Per-connection auth (not just first message); per-connection resource caps; back-pressure / max-queue; idle timeout; audit of connection lifecycle	V3.1, V9.1, V11.1.4	"Streaming gaps"
"AI/LLM-backed feature"	Prompt-injection handling at trust boundary; output validation before downstream side effects; per-actor rate limit and cost cap; audit log of prompts and tool calls; PII redaction policy	V11.1, V12.1, V8.1	"LLM boundary gaps"

When a feature triggers one of these patterns, prefill the corresponding requirements as Missing in the coverage matrix unless the PRD explicitly addresses them — most of the time it doesn't.

Output Templates

A. ASVS Level Decision

markdown

## ASVS Level Decision

**Chosen Level**: [1 | 2 | 3]

**Rationale**: [2–4 sentences. Cover data sensitivity, user population, regulatory context, and material-impact reasoning. Note why lower levels are insufficient if Level > 1.]

**Feature-Level Escalations**: [List any features that need a higher level than baseline, with one-line justification, or "None".]

B. Coverage Matrix

markdown

## Feature ↔ ASVS Coverage Matrix

| Feature | ASVS Section | Requirement ID | Level | Coverage | PRD Change Needed |
|---------|--------------|----------------|-------|----------|-------------------|
| F-01    | V2.2         | 2.2.1          | 2     | Missing  | Add MFA requirement for high-risk actions |
| F-01    | V7.1         | 7.1.1          | 2     | Partial  | Specify which auth events are logged |
| F-02    | V12.1        | 12.1.1         | 2     | Covered  | — |

Aim for completeness over brevity here — every feature × every applicable requirement gets a row. Where the gap pattern table applies, include the named requirements it surfaces.

C. Enhanced Feature Specifications

For each feature, emit exactly this shape:

markdown

### Feature F-01: [Title]

**Actor**: [user role / system]
**Data**: [data classes touched]
**Trust Boundaries**: [boundaries crossed]

**ASVS Mapping**: V2.2.1, V7.1.1, ...

**Updated Requirements**:
- [Original requirement, kept or rewritten]
- [Newly added requirement from ASVS mapping]
- [Newly added requirement from ASVS mapping]

**Acceptance Criteria**:
- [Testable criterion tied to a requirement above]
- [Testable criterion tied to a requirement above]

**Securability Notes**: [Short paragraph — only material SSEM/FIASSE points for this feature. Do not enumerate all attributes.]

D. Cross-Cutting Securability Requirements

Controls that span multiple features (centralized logging, secrets management, dependency policy, baseline TLS, error-handling standards). One bullet each, with the ASVS reference.

E. Open Gaps and Assumptions

Anything you could not resolve from the input: missing system context, unclear data sensitivity, unstated user populations, deferred decisions. Be explicit so the team can close these before implementation.

Worked Example (Mini)

Input feature (from a PRD):

F-03: Users can reset their password by clicking "Forgot Password" and entering their email. The system emails a reset link.

This trips the "Reset flow gaps" pattern in the gap table — so the missing requirements are predictable.

Enhanced output:

markdown

### Feature F-03: Password Reset via Email

**Actor**: Unauthenticated user (claiming an account)
**Data**: Email address (PII), password (credential), reset token
**Trust Boundaries**: browser → public API; API → email provider; API → credential store

**ASVS Mapping**: V2.2.2, V6.2.1, V6.2.2, V7.1.1, V11.1.4, V12.1.1

**Updated Requirements**:
- User can request a password reset by entering an account email at `/reset`.
- The system always returns the same success response whether or not the email matches an account (prevents account enumeration, V2.2.2).
- Reset tokens are single-use, expire within 15 minutes, and are stored only as a salted hash (V6.2).
- New passwords are validated against a minimum policy and screened against a known-breached-password list (V6.2.1).
- All reset requests, token issuances, token redemptions, and password changes are logged with user ID, source IP, user agent, and outcome (V7.1.1).
- Reset requests are rate-limited per email and per source IP (V11.1.4).
- The email input is canonicalized and validated against a strict format (V12.1.1).

**Acceptance Criteria**:
- Submitting a non-existent email returns the same response body, status code, and timing characteristics as a valid email (within tolerance).
- A reset token cannot be redeemed after 15 minutes or after first successful use; both cases produce a generic failure response and a logged `reset_token_invalid` event.
- More than 5 reset requests for the same email within 10 minutes are rejected with HTTP 429 and logged.
- Audit log lines for reset events are queryable by user ID and contain the fields above.

**Securability Notes**: This feature crosses an unauthenticated trust boundary (FIASSE v1.0.4 S4.3), so input handling and rate limiting are the load-bearing concerns. The reset token is server-owned state; never accept client-supplied token attributes beyond the opaque token itself (Derived Integrity, FIASSE v1.0.4 S4.4.1.2). Centralize token generation, hashing, and verification in a single module so the policy can evolve without touching call sites (Modifiability). All reset events must be observable in the audit pipeline so abuse patterns can be detected (Accountability + Observability, FIASSE v1.0.4 S3.2.1.4; Transparency S2.5).

This is the level of specificity the output should hit — concrete, testable, and traceable back to ASVS.

Quality Checklist (run before emitting)

Coverage

Every feature has an ID, actor, data classification, and trust-boundary list
ASVS level is chosen and justified before per-feature mapping
Every feature mapped against all applicable ASVS chapters at the chosen level
Gap patterns from the table above were applied to every relevant feature
Every Missing/Partial item produced a concrete PRD change

Output discipline

Coverage matrix is present and includes change-needed column
Each feature follows the exact output shape (Actor / Data / Trust Boundaries / ASVS Mapping / Updated Requirements / Acceptance Criteria / Securability Notes)
Acceptance criteria are behaviorally testable, not aspirational
Securability Notes are surgical — only material SSEM/FIASSE points, not exhaustive enumeration

Traceability

Every added requirement cites its ASVS reference
Cross-cutting requirements section captures shared controls
Open gaps and assumptions are listed explicitly

When in doubt

Prefer adding a missing requirement over assuming coverage; mark it explicitly so reviewers see it.
Prefer fewer, sharper ASVS references per feature over a long list that nobody will action.
Prefer plain language in Securability Notes — these are read by product managers, not just security engineers.

Reference Material

Step-by-step runbook: plays/prd-fiasse-asvs-enhancement.md
ASVS chapter index:
```
data/asvs/README.md
```
ASVS requirements (per chapter):
```
data/asvs/V*.md
```
FIASSE v1.0.4 foundational principles:
```
data/fiasse/S2.1.md
```
–
```
S2.6.md
```
(Transparency S2.5, Least Astonishment S2.6)
FIASSE v1.0.4 SSEM attribute umbrellas:
```
data/fiasse/S3.2.1.md
```
–
```
S3.2.3.md
```
; leaf files (e.g.
```
S3.2.1.4.md
```
Observability) for attribute-specific guidance
FIASSE v1.0.4 Boundary Control and Resilient Coding:
```
data/fiasse/S4.3.md
```
,
```
S4.4.md
```
, and the canonical-input-handling leaves
```
S4.4.1.md
```
,
```
S4.4.1.1.md
```
,
```
S4.4.1.2.md
```
FIASSE v1.0.4 Dependency Management and Stewardship:
```
data/fiasse/S4.5.md
```
,
```
S4.6.md
```

prd-securability-enhancement

NPX Install

Tags

SKILL.md Content

PRD Securability Enhancement (FIASSE/SSEM + ASVS)

When to Invoke

Inputs

Procedure

Step 1 — Parse features

Step 2 — Choose the ASVS level first

Step 3 — Map each feature to ASVS

Step 4 — Add Securability Notes per feature

Step 5 — Convert into testable acceptance criteria

Step 6 — Emit the enhanced PRD artifact

ASVS Coverage Gap Pattern Table

Output Templates

A. ASVS Level Decision

B. Coverage Matrix

C. Enhanced Feature Specifications

D. Cross-Cutting Securability Requirements

E. Open Gaps and Assumptions

Worked Example (Mini)

Quality Checklist (run before emitting)

When in doubt

Reference Material