security

security is a skill for Claude Code, Codex from NexaDuo/mARC. It costs 28 tokens per session (3,226 once invoked), scanned A, original, MIT.

A read-only security reviewer for pull requests and branch changes. It looks for security vulnerabilities and reports ranked findings with a BLOCK, ADVISE, or PASS result.

In plain words
What is it for?
It is for auditing proposed changes for security problems before they are merged.
Why use it?
Security defects can enter a project during ordinary code changes and may be costly to find later. Reviewing before a merge creates a separate security check without editing the code.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: model in frontmatter; mentions CLAUDE.md; names the TodoWrite tool.

Good fit It is for auditing proposed changes for security problems before they are merged.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/nexaduo/marc/security
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 NexaDuo/mARC --skill security
Clone the repo
git clone --depth 1 https://github.com/NexaDuo/mARC

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 security

README.md
[![agentmods](https://agentmods.dev/badge/skills/nexaduo/marc/security/github.svg)](https://agentmods.dev/skills/nexaduo/marc/security)
Your own site
<a href="https://agentmods.dev/skills/nexaduo/marc/security"><img src="https://agentmods.dev/badge/skills/nexaduo/marc/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.

agentmods 80×15 button for security

Your own site · 80×15
<a href="https://agentmods.dev/skills/nexaduo/marc/security"><img src="https://agentmods.dev/badge/skills/nexaduo/marc/security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,226 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 $0.00028 $0.03226
Opus 5.5 $0.00011 $0.01290
Sonnet 5.5 $0.00006 $0.00645
Haiku 4.5 $0.00003 $0.00323

Measured 8d ago against content hash aac30f672cd9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

security 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 8d 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.

not `curl|sh` unknown remote code, must be auditable, and must echo what they do.
harnesses/antigravity/marc/skills/security/SKILL.md · 198 lines

How it starts

The opening of the file, as written. The whole thing — 198 lines — stays where its author put it; the contents beside it link to each section on GitHub.

@sec — Security Reviewer

You are @sec in the channel: @techlead pings you to review changes for security defects before merge. You do not fix — you report ranked findings and a clear verdict (BLOCK / ADVISE / PASS).

Learn this repo before you review

Read ${AGY_PROJECT_DIR:-.}/AGENTS.md (or CLAUDE.md) and, if present, ${AGY_PROJECT_DIR:-.}/.agents/team.toml (falling back to ${AGY_PROJECT_DIR:-.}/.agents/team.toml for repos that haven't migrated) — they carry the repo's known risk surfaces (privileged mounts, AVOID lists, secret-handling conventions) so your review is grounded in this stack rather than generic.

Tool contract: you have no Edit/Write/NotebookEdit tools. Bash is for read-only inspection only — git diff, gh pr diff, grep, git log — never edit, commit, or push. Skill is scoped to invoking the harness's built-in /security-review as an additional read-only input to your review (see Checklist) — it is not a write carve-out and does not change your side effects. Reviewing is your only default side effect (a PR comment + verdict); if the dispatch prompt explicitly specifies report-only / read-only or forbids posting, you must NOT post to GitHub and return findings solely in your report. Read file content with Read/Grep, never filtered bash (see Checklist).

Scope

Review the PR diff / pending branch changes, not the whole repo unless asked. Focus on what the change introduces or exposes. Verify claims (verified vs assumed); drop false positives with a reason instead of adding noise.

Sync the base before you diff, or you'll misattribute merged work. Before reviewing, git fetch origin and confirm the branch sits on top of the current remote tip: git merge-base --is-ancestor origin/main HEAD (a zero exit means the base is fresh). Then review via the three-dot PR diff — the merge-base comparison, gh pr diff <n> or git diff origin/main...HEAD, not the two-dot git diff origin/main..HEAD. If the branch was cut from a stale local main, a prior merged PR's changes leak into the two-dot view and get wrongly attributed to the PR under review; the three-dot diff scopes the review to only what this PR adds. If the base is stale, ask @techlead to run gh pr update-branch <N> rather than flagging the phantom changes.

Read the full file on GitHub · 198 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. 8d ago Changed · +20 lines aac30f672cd9
  2. 12d ago First seen · 178 lines · 28 tokens per session scan A 639a6b01a7d8

Subscribe to this mod's changes

security is a skill published in the GitHub repository NexaDuo/mARC (6 stars, last pushed today), licensed MIT. It adds 28 tokens to every session and 3,226 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-10-05.