A guide for applying security practices while building or hardening backend, frontend, database, infrastructure, and operations code.

Use it for secure feature implementation, stack-specific hardening, security patterns, or a deployment security checklist.

It helps identify security concerns that depend on the technology stack and the kind of code being changed.

How matteocervelli/llms configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to matteocervelli/llms. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/matteocervelli/llms/main/.claude/skills/security/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/matteocervelli/llms

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/matteocervelli/llms/security.svg)](https://agentmods.dev/skills/matteocervelli/llms/security)

Your own site

<a href="https://agentmods.dev/skills/matteocervelli/llms/security"><img src="https://agentmods.dev/badge/skills/matteocervelli/llms/security.svg" alt="Measured on agentmods" height="20"></a>

Per session 75 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,054 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00075	$0.01054
Opus 5	$0.00037	$0.00527
Sonnet 5	$0.00015	$0.00211
Haiku 4.5	$0.00007	$0.00105

Measured 3d ago against content hash f83c051f3955, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

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 3d 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.

.claude/skills/security/SKILL.md · 122 lines

How it starts

The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security — Implementation SOPs

Unified security guidance for your stack. Auto-detects context from edited files or accepts explicit mode.

Usage

/security                     # Auto-detect stack from git changes
/security backend             # Explicit: FastAPI + SQLAlchemy + Redis
/security frontend            # Explicit: Jinja2 + HTMX + TypeScript/Vite
/security database            # Explicit: PostgreSQL + pgvector + Redis
/security infrastructure      # Explicit: Docker + Nginx + Cloudflare
/security operations          # Explicit: Deployment + secrets + monitoring
/security matrix              # Cross-reference matrix (L1/L2/L3)
/security checklist           # L1 essential pre-deployment checklist

Workflow

Step 1: Determine Context

Parse $ARGUMENTS for explicit mode. If no arguments provided, detect context:

DETECTED=$(bash "$HOME/.claude/skills/security/lib/context-detector.sh")

Step 2: Show Relevant Guidance

Based on detected or explicit mode, use progressive disclosure:

Level 1 — Summary (default, ~10 lines): Show the summary template for the detected stack. This is the entry point.

Level 2 — Patterns (on request, ~50 lines): When user asks for more detail, patterns, or "Don't/Do/Best" examples, show the patterns template.

Level 3 — Full SOP (on request, ~500-1100 lines): When user asks for the complete SOP, read the full source skill file.

Step 3: Handle Multiple Stacks

If context-detector returns multiple stacks (e.g., "backend,frontend"):

Show summary for each detected stack
Let user choose which to dive deeper into

Step 4: No Context Detected

If detection returns "none" and no explicit mode:

Show the matrix template as overview
List available modes for user to choose

Template Locations

Summary Templates (~10 lines each)

Mode	File
backend	`~/.claude/skills/security/templates/backend/summary.md`
frontend	`~/.claude/skills/security/templates/frontend/summary.md`
database	`~/.claude/skills/security/templates/database/summary.md`
infrastructure	`~/.claude/skills/security/templates/infrastructure/summary.md`
operations	`~/.claude/skills/security/templates/operations/summary.md`

Read the full file on GitHub · 122 lines

Files

What ships with it

12 files 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.

3d ago First seen · 122 lines · 75 tokens per session scan A f83c051f3955

Subscribe to this mod's changes

security is a skill published in the GitHub repository matteocervelli/llms (25 stars, last pushed 3mo ago), licensed MIT. It adds 75 tokens to every session and 1,054 once invoked, about $0.0004 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 2026-09-03.

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llms: Skill for Claude Code