Nuxt Fullstack Security Review

Nuxt Fullstack Security Review

Purpose

Review Nuxt 3/4 full-stack code — nuxt.config.ts, composables/, plugins/, server/api/, server/routes/, server/middleware/, and templates using useState/v-html — for five defect classes Nuxt's own documentation and its long-lived Nitro server model make security-critical: (a) private secrets placed under runtimeConfig.public (or fed by NUXT_PUBLIC_* env vars) so they ship in the client bundle, (b) useState/module-scope reactive or mutable state leaking across requests in Nitro's single long-lived process, (c) server-route SSRF via $fetch/ofetch to a user-controlled URL and blind forwarding of useRequestHeaders()/credentials, (d) NuxtPayload/useState data reaching an unsanitized render sink (XSS), and (e) missing security response headers (routeRules headers, the nuxt-security module, useResponseHeader). This skill exists so the review stays anchored to these five documented, structural defect classes instead of drifting into a general "Nuxt code review."

When to use

Use this skill when the user asks to:

• review a Nuxt nuxt.config.ts runtimeConfig/routeRules block for secret-exposure or missing-header risk,
• review a server/api/* or server/routes/* handler that calls out to another service ($fetch/ofetch/event.$fetch),
• investigate a report of one user seeing another user's data from a Nuxt app — the classic cross-request state pollution symptom,
• assess whether a useState/payload value rendered with v-html is safe,
• perform a pre-launch security review of a Nuxt 3/4 full-stack application.

Do not use this skill for:

• a Nuxt app's client-only component architecture, composable-extraction quality, or reactivity-boundary design with no security angle — use vue-composition-api-architecture-review instead,
• general Vue SSR concerns (non-Nuxt entry-server.js, raw @vue/server-renderer usage) with no Nuxt-specific API involved — use vue-ssr-security-review instead,
• Vuex/Pinia store internals or Vue Router navigation-guard security with no Nuxt-specific runtimeConfig/server//useState surface — use vue-state-store-security-review or vue-router-navigation-security-review instead,
• a bug that requires live traffic reproduction (concurrent-request load testing, a captured cross-user response, an actual SSRF probe against a running deployment) to confirm exploitation — static analysis proves the structural risk, not that it has already been exploited in production.

Context7 Documentation Protocol

• Resolve and query /websites/nuxt_4_x (primary; Nuxt 4 prose docs) and /websites/nuxt_3_x (Nuxt 3 prose docs) before citing any runtimeConfig, useState, $fetch/event.$fetch/useRequestFetch/useRequestHeaders, payload/devalue, routeRules, or useResponseHeader behavior as fact. Both are Nuxt's own documentation site content mirrored into Context7 — treat matches from either as documentation-based.
• Confirm which Nuxt major the target repo uses (package.json's nuxt dependency) before assuming version-specific defaults; the APIs this skill covers are stable across 3/4, but state which major was confirmed when citing a claim.
• The third-party nuxt-security module's exact default header set and configuration surface is not covered by Nuxt's own Context7-indexed docs — never state a specific default for it as documentation-based. Confirm its presence/config by reading the repo's nuxt.config.ts directly, and label any claim about its behavior inference unless corroborated by the module's own documentation (not currently in scope for this skill's Context7 grounding).
• Do not invent API names. If Context7 does not confirm an API or default, say so explicitly and label the claim inference.
• If Context7 is unavailable, fall back to the official_docs URLs in this skill's metadata.json and label the claim documentation-based, unverified against current release.

Lean operating rules

• Every finding in this skill's five defect classes defaults to HIGH severity (missing-security-headers may be MEDIUM-to-HIGH depending on the app's actual surface — see references/ssrf-payload-and-response-headers.md, Part 3). Do not downgrade a structural runtimeConfig exposure, cross-request state leak, SSRF path, or payload-XSS trace to informational because it has not been observed exploited yet.
• Trace every finding to a concrete file:line and a concrete data-flow path. A finding that says "this might leak the secret" or "this fetch call could be SSRF" without showing the specific config key, the specific module-scope declaration and its reachability, or the specific origin-to-sink trace is a guess, not a finding.
• Classify every runtimeConfig key by its actual nesting (top-level = private, under public = client-exposed) — never by variable name alone. A key named apiSecret sitting inside public is exposed; a key named baseUrl sitting outside public is still private and not itself a finding.
• Classify every module-scope declaration on two axes before flagging it: mutability/reactivity (only useState/ref/reactive/mutable objects are at risk; immutable constants are not), and reachability from server-rendered code (a declaration no server-rendered path ever touches is not a finding in this scope).
• Do not clear a $fetch/ofetch/event.$fetch call in a server route as safe from SSRF just because it "looks like an API call" — trace the destination URL to its origin and confirm either a hardcoded host or an explicit allowlist check before the request fires.
• Do not clear a header-forwarding call (event.$fetch's default forwarding, useRequestHeaders(...), or manual header spreading) as safe just because Nuxt documents the mechanism — the mechanism existing is not the same as its use being scoped to only the headers actually needed and only trusted destinations.
• Do not approve a useState/payload value reaching a v-html binding unless a named sanitizer call is visibly present on that exact traced path — a sanitizer existing elsewhere in the codebase does not clear this bar.
• Do not report "no security headers" as cleared just because a mechanism exists somewhere in the config — confirm the routeRules glob (or module config) actually covers the routes in scope before crediting it.
• Never execute, build, or run application code, and never send live requests, as part of this review; this is a static-review skill (Read/Grep/Glob only).
• Load only the reference needed for the concern in scope.

References

Load these only when needed:

• Review workflow and findings contract — use for the step-by-step review procedure, the full decision tree across all five defect classes, and the required output shape.
• runtimeConfig exposure and cross-request state pollution — load when reviewing nuxt.config.ts's runtimeConfig block, NUXT_PUBLIC_* env vars, or useState/module-scope reactive/mutable declarations reachable from server-rendered code.
• Server-route SSRF, header forwarding, payload XSS, and missing response headers — load when reviewing a server/api/server/routes handler's outbound $fetch/ofetch/event.$fetch/useRequestFetch calls, a useState/payload value that renders somewhere, or routeRules/security-module configuration.
• Acceptance rubric — the authoritative list of defects this skill must catch and the false positives it must not raise; consult when unsure whether a pattern is in scope.

Response minimum

Return, at minimum:

• the runtimeConfig/routeRules blocks, module-scope declarations, server routes, and/or template bindings in scope,
• ranked findings with file:line evidence, defect category (runtimeconfig-exposure / cross-request-state-pollution / ssrf / credential-forwarding / payload-xss / missing-security-headers), the concrete data-flow trace, and a fix sketch matching Nuxt's documented pattern,
• for every useState/payload → render-sink finding, an explicit statement of whether a sanitizer call is present on the traced path — never approve on the assumption one exists elsewhere,
• evidence level per finding (repo evidence, documentation-based, or inference), with structural risk findings explicitly labeled as structural risk, not as confirmed-exploited,
• verdict (approve / approve-with-notes / block),
• open questions or scope the review could not cover (e.g., "confirming actual cross-request leakage requires concurrent-request load testing, not static review").