security-review

Security Review

Use this skill when reviewing or planning code that touches a security-sensitive
surface in Langfuse. It collects the recurring findings the team has seen in
external security reports so that future agents catch them at design and review
time rather than after the fact.

When to Apply

Apply this skill when the change touches any of:

• a user-supplied URL, host, endpoint, baseURL, or webhook target
• a new outbound HTTP request (fetch, axios, AWS SDK client init with a
  custom endpoint, OpenAI/Anthropic/Bedrock client init with a custom
  baseURL, etc.)
• a new integration form under Settings -> Integrations or any
  admin-configurable network destination
• a new tRPC procedure or public API route that mutates project-scoped data or
  changes who can access it
• secrets, API keys, signing secrets, or encryption-at-rest fields
• redirect-following or cross-origin header handling
• file uploads, image proxies, or other binary data flowing in or out
• product analytics, browser monitoring, session replay, or another client-side
  telemetry path that can transmit customer-controlled content

Apply this skill during plan mode when designing a new integration so the
correct validation surfaces land in the plan, not in a follow-up CVE.

How to Read This Skill

1. Open references/checklist.md and run the mental
   sweep against the change.
2. For each bullet that fires, open the matching topic reference.

Topic	Open when	File
SSRF and outbound URL validation	The change accepts or fetches a user-supplied URL, host, or endpoint	references/outbound-url-validation.md
Secret read paths	The change shapes what a read route returns for an entity or config blob that also stores a credential	references/secret-read-paths.md
Client telemetry and session replay	The change records DOM, browser state, events, logs, or network data in a third-party system	references/client-telemetry-privacy.md

The catalog is intentionally short today. New topic files are added as new
finding classes recur (see "Extending This Skill").

Output Expectations (Review Mode)

When this skill is used during code review:

• List findings first, ordered by severity, with file and line references.
• For each finding, name the canonical helper or known-good call site the
  author should copy.
• For SSRF-class findings, point at references/outbound-url-validation.md
  rather than re-deriving the fix.
• Call out missing negative tests (private-IP, cross-tenant, missing-scope)
  as findings, not as nice-to-haves.

Output Expectations (Design / Plan Mode)

When this skill is used while planning:

• Restate which surfaces the new feature exposes (forms, public API routes,
  worker entrypoints).
• For each surface that matches a checklist trigger, name the validator or
  helper that must be invoked and at which layer (save-time, use-time,
  connection-time, redirect-time).
• Treat "we will validate later" as a design defect: validation belongs in the
  same change that introduces the surface.

Extending This Skill

Add a new references/<topic>.md whenever a security finding recurs across
features or PR reviews. Keep each reference narrow and concrete:

1. Threat in plain language (one paragraph).
2. Canonical helpers in this repo, with paths.
3. Known-good call sites that can be copied.
4. Required defenses (save-time, use-time, transport-time, etc.).
5. Anti-patterns to flag in review.

Then add a one-line trigger to references/checklist.md
pointing at the new topic file, and add a row to the table above.

Candidates for future references (do not add until a real finding recurs):

• Tenant isolation (projectId filters across Prisma and ClickHouse)
• Redirect mishandling and sensitive-header propagation
• File upload validation and content-type sniffing
• RBAC scope drift on new tRPC/public API endpoints
• Signed URL scoping (expiry, path, method)
• Public API rate limiting and auth boundary checks

Integration With Other Skills

• The shared code-review skill should defer here for any change that matches
  the triggers above; see code-review/SKILL.md.
• The shared backend-dev-guidelines skill should defer here when adding
  outbound HTTP, integration config, or URL-accepting procedures; see
  backend-dev-guidelines/SKILL.md.
• Confirmed issues with reproduction evidence go through linear-bug-triage
  for Linear handoff.