common-llm-security

common-llm-security is a skill for Claude Code, Codex from HoangNguyen0403/agent-skills-standard. It costs 56 tokens per session (705 once invoked), scanned A, original, MIT.

A checklist for securing applications that use large language models (LLMs), including chat systems, AI agents, prompts, tools, and retrieval systems. It covers risks such as prompt injection, leaked information, unsafe tool use, and untrusted third-party components.

In plain words
What is it for?
Use it to review AI client code, agent workflows, prompt templates, tool permissions, retrieved documents, and logging or storage of sensitive information.
Why use it?
It helps identify security problems that are specific to AI applications and may not appear in ordinary web security checks. It places early attention on user-controlled input and tools that can change data or run commands.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to review AI client code, agent workflows, prompt templates, tool permissions, retrieved documents, and logging or storage of sensitive information.

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Install with agentmods
npx agentmods add skills/hoangnguyen0403/agent-skills-standard/common-llm-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 HoangNguyen0403/agent-skills-standard --skill common-llm-security
Clone the repo
git clone --depth 1 https://github.com/HoangNguyen0403/agent-skills-standard

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 common-llm-security

README.md
[![agentmods](https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/common-llm-security/github.svg)](https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/common-llm-security)
Your own site
<a href="https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/common-llm-security"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/common-llm-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 common-llm-security

Your own site · 80×15
<a href="https://agentmods.dev/skills/hoangnguyen0403/agent-skills-standard/common-llm-security"><img src="https://agentmods.dev/badge/skills/hoangnguyen0403/agent-skills-standard/common-llm-security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 705 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 24
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
  • medium Excessive Agency · line 41
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
How audits are shown
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 $0.00056 $0.00705
Opus 5 $0.00028 $0.00352
Sonnet 5 $0.00011 $0.00141
Haiku 4.5 $0.00006 $0.00071

Measured 12d ago against content hash eea5bf8560c3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

common-llm-security 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 12d 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.

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.

.agents/skills/common/common-llm-security/SKILL.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OWASP LLM Top 10 Security Checklist (2025)

Priority: P0 (CRITICAL)

Implementation Guidelines

  • Check LLM01 first: Prompt injection #1 LLM finding — any user input concatenated directly into prompt string immediate P0.
  • Check LLM06 next: Agent tools with write/delete/execute capabilities without confirmation P0.
  • Mark each item: ✅ not affected | ⚠️ needs review | 🔴 confirmed finding.
  • P0 finding caps Security score at 40/100 — not skip any item.
  • See references/owasp-llm.md for full detection signals.

OWASP LLM Top 10 (2025)

ID Risk Key Detection Signal
LLM01 Prompt Injection User input string-concatenated into prompt. Retrieved docs inserted into system turn.
LLM02 Sensitive Information Disclosure PII or credentials passed into prompt context. LLM response logged without redaction.
LLM03 Supply Chain Unverified model weights or plugins. Third-party agent added without trust review.
LLM04 Data & Model Poisoning User-controlled data written to training sets or embedding stores without validation.
LLM05 Improper Output Handling LLM output used directly in DOM sink, SQL query, shell command, or redirect URL.
LLM06 Excessive Agency Agent tool with write/delete/network access — no human-in--loop confirmation.
LLM07 System Prompt Leakage System prompt content returned via tool output, error message, or API response.
LLM08 Vector & Embedding Weaknesses User text injected into vector store without sanitization. No tenant namespace isolation.
LLM09 Misinformation LLM output used for critical decisions (medical, financial, legal) without verification.
LLM10 Unbounded Consumption No max_tokens on LLM call. No rate limit on invocations. Agent loop without depth cap.

Anti-Patterns

  • No prompt concat: Pass user input as separate user turn, never interpolated into system prompts.
  • No raw LLM output in sinks: Sanitize LLM responses before writing to DOM, queries, or shell.
  • No uncapped agent loops: Every agentic recursion must enforce max iteration/depth limit.

Read the full file on GitHub · 58 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 12d ago First seen · 58 lines · 56 tokens per session scan A eea5bf8560c3

Subscribe to this mod's changes

common-llm-security is a skill published in the GitHub repository HoangNguyen0403/agent-skills-standard (565 stars, last pushed 3d ago), licensed MIT. It adds 56 tokens to every session and 705 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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