Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add coldtatooine/vuln-skill-pack --skill nextjs-vercel-securitygit clone --depth 1 https://github.com/coldtatooine/vuln-skill-packWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/nextjs-vercel-security)<a href="https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/nextjs-vercel-security"><img src="https://agentmods.dev/badge/skills/coldtatooine/vuln-skill-pack/nextjs-vercel-security/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/nextjs-vercel-security"><img src="https://agentmods.dev/badge/skills/coldtatooine/vuln-skill-pack/nextjs-vercel-security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00056 | $0.00967 |
| Opus 5 | $0.00028 | $0.00483 |
| Sonnet 5 | $0.00011 | $0.00193 |
| Haiku 4.5 | $0.00006 | $0.00097 |
Grade B, and why
nextjs-vercel-security scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Cloud metadata endpointmediumServer-side request forgery
One request to 169.254.169.254 can return temporary IAM credentials.
- Server-side `fetch()` with a user-supplied URL → SSRF into internal services / cloud metadata (`169.254.169.254`). Allowlist hosts. Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
How it starts
The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Next.js & Vercel Security Footguns
Apply this when the codebase uses Next.js (App or Pages Router) or deploys to Vercel. These are the high-frequency holes; pair with /scan, /preflight, and /secrets.
Verify before flagging
NEXT_PUBLIC_*with publishable/anon/pk_keys is expected — only flag real secrets (service_role,sk_, DB URLs, JWT secrets).- Middleware matcher gaps need a concrete uncovered protected path, not a vague "matcher looks incomplete."
- A Server Action that verifies session + ownership is not "unauthenticated" just because it is a public POST endpoint by design.
- CDN/edge caching is only a finding when authenticated or user-specific responses can be cached and shared.
1. Secret leakage across the client/server boundary
NEXT_PUBLIC_*is public. Anything with this prefix is inlined into the JS bundle and shipped to the browser. A real secret here = leaked secret. Only publishable/anon keys belong here.- Server-only secrets must never be imported into a Client Component. A module imported by a
"use client"file (directly or transitively) ships to the browser. Check import chains, not just the file. server-onlypackage: server code that must never reach the client shouldimport 'server-only'to fail the build if it does.- Supabase
service_role, Stripesk_*, DB URLs → server only.
2. Server Actions
- Every Server Action is a public POST endpoint. No auth is applied automatically. Each action must independently verify session AND authorization — do not assume it's only callable from your UI.
- Origin / CSRF posture: confirm actions check a trusted origin (or equivalent framework protection) and a valid session before mutating state.
- Validate and authorize arguments. Args are attacker-controlled. Re-check ownership/tenant on every ID passed in. Don't trust hidden form fields.
- Actions defined inline in a Server Component are still individually invocable.
3. Route Handlers (route.ts) & API routes
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 64 lines · 0 tokens per session scan B 1036d5bc8d47
nextjs-vercel-security is a skill published in the GitHub repository coldtatooine/vuln-skill-pack (2 stars, last pushed 15d ago), licensed MIT. It adds 56 tokens to every session and 967 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it B with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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