yds-vulnerability-scan

yds-vulnerability-scan is a skill for Claude Code, Codex from ymd38/dev-skills. It costs 127 tokens per session (3,347 once invoked), scanned A, original, MIT.

A read-only security audit based on the Open Worldwide Application Security Project (OWASP) risks, using Semgrep plus manual review.

In plain words
What is it for?
It checks for access-control errors, injection, browser-security problems, server-side request forgery (SSRF), exposed secrets, and personal-data leaks.
Why use it?
It finds common security weaknesses and explains their evidence and possible attack paths without changing the code.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit It checks for access-control errors, injection, browser-security problems, server-side request forgery (SSRF)…

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Install with agentmods
npx agentmods add skills/ymd38/dev-skills/yds-vulnerability-scan
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.

Any agent
npx skills add ymd38/dev-skills --skill yds-vulnerability-scan
Clone the repo
git clone --depth 1 https://github.com/ymd38/dev-skills

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for yds-vulnerability-scan

README.md
[![agentmods](https://agentmods.dev/badge/skills/ymd38/dev-skills/yds-vulnerability-scan.svg)](https://agentmods.dev/skills/ymd38/dev-skills/yds-vulnerability-scan)
Your own site
<a href="https://agentmods.dev/skills/ymd38/dev-skills/yds-vulnerability-scan"><img src="https://agentmods.dev/badge/skills/ymd38/dev-skills/yds-vulnerability-scan.svg" alt="Measured on agentmods" height="20"></a>
Per session 127 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,347 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found 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 5.1 $0.00127 $0.03347
Opus 5 $0.00063 $0.01673
Sonnet 5 $0.00025 $0.00669
Haiku 4.5 $0.00013 $0.00335

Measured 6d ago against content hash 23ea47c4e395, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

yds-vulnerability-scan scanned grade A 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 6d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- All endpoints that fetch user-supplied URLs (`fetch(req.body.url)`, `requests.get(url)`)
skills/yds-vulnerability-scan/SKILL.md · 356 lines

How it starts

The opening of the file, as written. The whole thing — 356 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Role: Offensive Security Auditor (Defense-Focused)

You perform systematic, evidence-based security audits with an attacker's mindset and a defender's output. Your findings are grounded in specific file/line citations. Every reported vulnerability has a clear attack path, a justified severity, and a concrete remediation recommendation. This is a read-only inspection — you do NOT modify any code.


Phase 1: Scope & Context

1.1 Pre-Scan Checklist

Before scanning, identify:

  1. Language & runtime — determines which injection patterns and tooling apply
  2. Trust boundaries — where does untrusted input enter the system? (HTTP params, headers, file uploads, message queues, webhooks)
  3. Authentication model — JWT, session cookies, API keys, OAuth?
  4. Data sensitivity — PII, financial data, credentials, health data?
  5. Deployment context — public internet? internal only? multi-tenant?

Context determines severity weighting. A missing HttpOnly flag on an internal admin tool is Medium; on a public banking app it is High.

1.2 Scan Strategy: Two Layers

Security audits require both automated scanning and manual review. Automated tools miss logic flaws; manual review misses patterns at scale. Do both.

Layer 1 — Automated (Semgrep)

semgrep --config auto --json --output semgrep-results.json .

Parse results and triage each finding as True Positive or False Positive (see triage guide in Phase 2).

Layer 2 — Manual Review After automated scanning, manually inspect the following high-risk areas that tools routinely miss:

  • Authorization logic (can user A access user B's resources?)
  • Business logic flows (can a free user access paid features?)
  • Race conditions in state-changing operations
  • Cryptographic implementation choices
  • Third-party dependency audit: npm audit / pip-audit / trivy / cargo audit

Phase 2: Vulnerability Checklist

Work through each category. For each, describe: what you searched for, what you found, and whether each finding is a true positive or false positive.

Read the full file on GitHub · 356 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. 6d ago First seen · 356 lines · 127 tokens per session scan A 23ea47c4e395

Subscribe to this mod's changes

yds-vulnerability-scan is a skill published in the GitHub repository ymd38/dev-skills (4 stars, last pushed 9d ago), licensed MIT. It adds 127 tokens to every session and 3,347 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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