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.
npx agentmods add skills/hkuds/deepcode/security-best-practicesnpx skills add HKUDS/DeepCode --skill security-best-practicesgit clone --depth 1 https://github.com/HKUDS/DeepCodeWhat 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 | $0.00073 | $0.01661 |
| Opus 5 | $0.00036 | $0.00830 |
| Sonnet 5 | $0.00015 | $0.00332 |
| Haiku 4.5 | $0.00007 | $0.00166 |
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 2d 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.
Copies of this mod
5 near-identical copies found in the catalogue:
- security-best-practices — 100% identical, 0 lines differ
- security-best-practices — 100% identical, 9 lines differ
- security-best-practices — 100% identical, 9 lines differ
- security-best-practices — 100% identical, 0 lines differ
- security-best-practices — 97% identical, 5 lines differ
How it starts
The opening of the file, as written. The whole thing — 87 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.
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.
- agents/openai.yaml 237 B
- LICENSE.txt 11 KB
- references/golang-general-backend-security.md 38 KB
- references/javascript-express-web-server-security.md 48 KB
- references/javascript-general-web-frontend-security.md 38 KB
- references/javascript-jquery-web-frontend-security.md 33 KB
- references/javascript-typescript-nextjs-web-server-security.md 42 KB
- references/javascript-typescript-react-web-frontend-security.md 41 KB
- references/javascript-typescript-vue-web-frontend-security.md 31 KB
- references/python-django-web-server-security.md 38 KB
- references/python-fastapi-web-server-security.md 44 KB
- references/python-flask-web-server-security.md 31 KB
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.
- 2d ago First seen · 87 lines · 73 tokens per session scan A 7b3dae1ffc54
security-best-practices is a skill published in the GitHub repository HKUDS/DeepCode (16,464 stars, last pushed 4d ago), licensed MIT. It adds 73 tokens to every session and 1,661 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 2026-08-30.
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