security-web

A security-review guide for TypeScript and JavaScript web applications. It covers risks such as cross-site scripting, forged requests, leaked secrets, broken permissions, injection, unsafe file handling, and requests to internal services.

In plain words
What is it for?
Use it when reviewing or securely implementing web frontends, backends, HTTP handlers, forms, file uploads, server actions, or outbound network requests.
Why use it?
It makes reviewers trace where untrusted data enters the system and where security decisions are enforced. This helps uncover vulnerabilities hidden by web frameworks or client-side checks.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/robconery/kolea/security-web
Any agent
npx skills add robconery/kolea --skill security-web
Clone the repo
git clone --depth 1 https://github.com/robconery/kolea

Made for: Claude Code, Codex.

Per session 207 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,019 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00207 $0.03019
Opus 5 $0.00103 $0.01510
Sonnet 5 $0.00041 $0.00604
Haiku 4.5 $0.00021 $0.00302

Measured 2d ago against content hash e9026350da7e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

security-web scanned grade A with 0 findings 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 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (templates/input-validation.ts), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to security-web — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/skills/security-web/SKILL.md · 208 lines

How it starts

The opening of the file, as written. The whole thing — 208 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web Application Security Review

Treat every byte that crossed a network boundary as hostile until proven otherwise, and prove it on the server. The client is an untrusted rendering surface you do not control. Frameworks add convenience (Server Actions, Nitro routes, Bun.serve, Hono middleware) that hides the trust boundary — this skill's job is to make the reviewer see the boundary the framework obscured.

🎯 Why: Design for Change

The goal of writing software is to be able to change it safely. Secure-by-default config (CSP, cookie flags, parameterized queries, authz-at-the-edge) means the next feature ships without re-litigating the threat model. Every insecure default you accept becomes a foothold the next change has to step around.

This skill is for security review and secure implementation. For general TypeScript correctness use typescript-best-practices; for schema-level integrity use postgres-dba. This skill never assumes another layer will catch it.

How to use this skill (review workflow)

  1. Map the attack surface first. Identify every trust boundary: HTTP handlers, Server Actions, form posts, websocket frames, file uploads, outbound fetches, postMessage, process.env reaching the client, third-party script tags. A vuln you didn't enumerate is a vuln you didn't find.
  2. Triage each input against the decision guide below; open the matching references/*.md for the exploit, the vulnerable pattern, the fix, and the false-positive caveat.
  3. Apply the framework reference (references/nextjs.md, nuxt.md, bun.md, hono.md) — the generic finding almost always has a framework-specific trap or a framework-specific fix.
  4. Report findings in the standard format (templates/finding.md): severity, location (file:line), a concrete exploit walkthrough, and the minimal fix. No exploit path stated → it is an observation, not a finding; say which.
  5. Recommend the secure default, not a bespoke patch. The templates/ configs (CSP, security headers, cookies, CORS) are the target state; a one-off escape is a stopgap.

Read the full file on GitHub · 208 lines

Changes

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.

  1. 2d ago First seen · 208 lines · 207 tokens per session scan A e9026350da7e

Subscribe to this mod's changes

security-web is a skill published in the GitHub repository robconery/kolea (1 stars, last pushed 2d ago), licensed MIT. It adds 207 tokens to every session and 3,019 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to security-web, differing in 0 lines, and is treated as a copy.

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