Security checklist

Pre-deployment security audit organized around the OWASP Top 10:2025 categories (released late 2025, succeeding the 2021 edition). This is the baseline that prevents obvious disasters — not a substitute for a real penetration test or threat model. For verification depth beyond this checklist, see OWASP ASVS 5.0 (https://owasp.org/www-project-application-security-verification-standard/). For API-specific scope, see OWASP API Security Top 10:2023 (https://owasp.org/API-Security/editions/2023/en/0x00-header/).

Step 0: Research the current security landscape (do this first)

Security knowledge ages on a 6-12 month half-life. The recipes below were last verified on 2026-05-08; they may be stale by the time you read this. Before applying any pattern in this skill, fan out research scoped to the OWASP Top 10:2025 categories being audited so the recipes are interpreted against current authoritative sources, not against this file's snapshot.

Default-on, with a documented skip

Run the 4-angle research below by default. Skip ONLY when ALL of these hold:

• (a) You ran this same skill on this same primitive within the last 4 hours of the current session,
• (b) That prior research surfaced no urgent advisories for the OWASP Top 10:2025 categories being audited,
• (c) You log a one-line Research skipped because <reason> note in your response.

"I think I know" / "moving fast" / "user wants this done quickly" / "already familiar" are NOT valid skip reasons. The whole point of this preamble is that future-you should not trust this skill body's defaults until current state is checked.

Fan out 4 subagents in parallel

Each subagent returns ≤300 words of bullets with citations. Dispatch all 4 in a single message so they run concurrently.

Angle 1 — Authoritative standards. Have NIST / OWASP / IETF (RFCs and Internet-Drafts) / W3C / CISA published anything new about the OWASP Top 10:2025 categories being audited in the last 6-12 months? Look for: spec finalizations, deprecations, replacement specs, RFC publications, draft revisions, NIST SP updates, OWASP project version bumps. Cite by document number + publication date.

Angle 2 — Active exploitation. What's actively being exploited that targets the OWASP Top 10:2025 categories being audited? Pull from: CISA Known Exploited Vulnerabilities (KEV) catalog (filter to last 6-12 months), recent CVE / GHSA entries with high CVSS or in-the-wild exploitation, breach postmortems and incident reports (CSRB, vendor RCAs, security-vendor research). Surface CWE patterns dominating recent KEV adds. Cite by CVE number + advisory URL.

Angle 3 — Tooling and library state. Are the libraries this skill recommends still current? What are the latest major versions in the relevant package registry (npm / PyPI / RubyGems / crates.io)? Have any been deprecated, replaced, or merged into another project? Have any flipped a secure default? Look up current versions in: registry.npmjs.org, pypi.org, rubygems.org, crates.io, pkg.go.dev. Cite by package + version + release date.

Angle 4 — Practitioner discourse. What are practitioners and security teams talking about in the last 6 months? Pull from: OWASP Cheat Sheet Series (last-modified date matters), GitHub Security Lab posts, vendor security blogs (Cloudflare, Fastly, Snyk, Datadog, Wiz, GitGuardian), conference talks (Black Hat, DEF CON, OWASP Global AppSec, USENIX Security), SANS ISC, Krebs, recent OWASP project re-releases. Surface the patterns being adopted and the anti-patterns being called out. Cite by post URL + author + date.

Synthesize before applying recipes

After the 4 returns land, write a 1-paragraph "current state for the OWASP Top 10:2025 categories being audited, as of <today's date>" that names:

• The current normative ceiling (what specs say SHOULD be the default in 2026).
• 1-2 active threats specific to the OWASP Top 10:2025 categories being audited from the last 6-12 months.
• Any tooling drift (deprecated lib, new default in a framework, package merged or replaced).
• Any practitioner consensus shift visible in recent cheat sheet / blog updates.

If the synthesis flags drift in this skill body's recipes (e.g., a spec finalized after 2026-05-08, a library now deprecated, a default flipped), call that out explicitly in your response and override the skill body where they conflict. The synthesis wins. The skill body is scaffolding, not scripture.

When you cannot run subagents

If subagents are not available in your runtime, the same shape applies in-line: do 4 sequential targeted searches (web search for standards, KEV catalog lookup, package registry version checks, recent cheat-sheet diff). Land the same 1-paragraph synthesis. Cost goes up; the protection does not change.

How to use this checklist

Walk all 10 categories before any production deployment. For each category: read the framing paragraph, run through the must-do items, and check the code-pattern references where they apply. After the walk, file findings as one issue per category with gaps. The flat 25-item Yes/No gate at the end is the pre-deploy summary, not the audit itself.

If you can't check an item, don't ship — fix it first.

A01:2025 — Broken Access Control

Authorization failures are the most-exploited class on the web. The 2025 edition folds SSRF (Server-Side Request Forgery) into A01 because the underlying failure is the same: the server acts on a request it should have rejected. Active exemplars in 2024-2025 include broken object-level authorization in API endpoints (still the dominant API risk per OWASP API Top 10:2023 API1) and SSRF used as a pivot to cloud metadata endpoints.

• Authorization checked at every endpoint, not just at the gateway or middleware layer.
• Default-deny at the controller level (explicit allow per route, not implicit allow).
• Object-level authorization on every resource fetch (IDOR — don't expose IDs without checking the principal owns them).
• Function-level authorization on admin and privileged endpoints (check role, not just route).
• SSRF defenses: outbound allowlist for any URL fetched server-side; no localhost, 127.0.0.0/8, link-local (169.254.0.0/16), or cloud metadata IP (169.254.169.254) fetches; DNS rebinding protection on resolvers.
• Database row-level security enabled where the platform supports it (see code-pattern below).
• Application uses a dedicated database user with minimum required permissions, not root/admin.

Code pattern: PostgreSQL / Supabase row-level security

-- Enable RLS on table
ALTER TABLE documents ENABLE ROW LEVEL SECURITY;

-- Users can only read their own documents
CREATE POLICY "Users can read own documents" ON documents
  FOR SELECT USING (auth.uid() = user_id);

-- Users can only insert documents as themselves
CREATE POLICY "Users can insert own documents" ON documents
  FOR INSERT WITH CHECK (auth.uid() = user_id);

-- Users can only update their own documents
CREATE POLICY "Users can update own documents" ON documents
  FOR UPDATE USING (auth.uid() = user_id);

-- Users can only delete their own documents
CREATE POLICY "Users can delete own documents" ON documents
  FOR DELETE USING (auth.uid() = user_id);

A02:2025 — Security Misconfiguration

Misconfiguration moved up the rankings (was A05 in 2021) because default-insecure framework settings keep shipping to production. The 2024 Snowflake / UNC5537 campaign is the canonical lesson: MFA was opt-in per tenant by default, and the campaign harvested credentials at scale before Snowflake flipped the default in 2024.

• Hardened images / minimal containers (distroless or slim base; no shells unless required).
• Default credentials removed; default ports closed at the firewall.
• CORS configured for specific origins (Access-Control-Allow-Origin: * flagged in production).
• Production-mode flag set on web frameworks: Flask debug=False, Dj