What is security-best-practices?

A guide for reviewing Python, JavaScript, and TypeScript code for common security problems and recommending safer coding practices.

It is for security reviews and secure-by-default coding advice in supported languages and frameworks.

It helps identify weaknesses before they become vulnerabilities in applications or services.

security-best-practices — Skill for Codex by PracticalSwan

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 PracticalSwan/agent-skills --skill security-best-practices

Clone the repo

git clone --depth 1 https://github.com/PracticalSwan/agent-skills

Made for: 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/practicalswan/agent-skills/security-best-practices/github.svg)](https://agentmods.dev/skills/practicalswan/agent-skills/security-best-practices)

Your own site

<a href="https://agentmods.dev/skills/practicalswan/agent-skills/security-best-practices"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/security-best-practices/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/practicalswan/agent-skills/security-best-practices"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/security-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,195 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.

Origin 86% 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.

Model	Per session	Once invoked
Fable 5.1	$0.00073	$0.02195
Opus 5	$0.00036	$0.01097
Sonnet 5	$0.00015	$0.00439
Haiku 4.5	$0.00007	$0.00219

Measured 4d ago against content hash 62f097ad683f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

security-best-practices 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 4d 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.

Origin

This is a copy

86% identical to security-best-practices — 54 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.

security-best-practices/SKILL.md · 137 lines

How it starts

The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Best Practices

Overview

This skill provides a description of how to identify the language and frameworks used by the current context, and then to load information from this skill's references directory about the security best practices for this language and or frameworks.

This information, if present, can be used to write new secure by default code, or to passively detect major issues within existing code, or (if requested by the user) provide a vulnerability report and suggest fixes.

Workflow

The initial step for this skill is to identify ALL languages and ALL frameworks which you are being asked to use or already exist in the scope of the project you are working in. Focus on the primary core frameworks. Often you will want to identify both frontend and backend languages and frameworks.

Then check this skill's references directory to see if there are any relevant documentation for the language and or frameworks. Make sure you read ALL reference files which relate to the specific framework or language. The format of the filenames is <language>-<framework>-<stack>-security.md. You should also check if there is a <language>-general-<stack>-security.md which is agnostic to the framework you may be using.

If working on a web application which includes a frontend and a backend, make sure you have checked for reference documents for BOTH the frontend and backend!

If you are asked to make a web app which will include both a frontend and backend, but the frontend framework is not specified, also check out javascript-general-web-frontend-security.md. It is important that you understand how to secure both the frontend and backend.

If no relevant information is available in the skill's references directory, think a little bit about what you know about the language, the framework, and all well known security best practices for it. If you are unsure you can try to search online for documentation on security best practices.

From there it can operate in a few ways.

Read the full file on GitHub · 137 lines

Files

What ships with it

13 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.

4d ago Changed 62f097ad683f
6d ago Changed d8a9d9288661
8d ago First seen · 137 lines · 73 tokens per session scan A ffeec83a5ba2

Subscribe to this mod's changes

security-best-practices is a skill published in the GitHub repository PracticalSwan/agent-skills (14 stars, last pushed 4d ago), licensed MIT. It adds 73 tokens to every session and 2,195 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to security-best-practices, differing in 54 lines, and is treated as a copy.

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