security

A baseline of rules for preventing common security flaws in software. It covers secrets, input validation, database and command injection, login and permission checks, data protection, and vulnerable dependencies.

In plain words
What is it for?
Use it while writing or reviewing code that handles external input, accounts, permissions, personal data, secrets, databases, shell commands, or third-party packages.
Why use it?
It gives everyday coding decisions a consistent safety standard and helps avoid weaknesses that attackers commonly exploit.

Cursor rule

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.

agentmods
npx agentmods add rules/dasomel/oh-my-cursor/security
Clone the repo
git clone --depth 1 https://github.com/dasomel/oh-my-cursor
Per session 331 This file is loaded in full into every session.
When invoked 331 The same file — it is already loaded in full.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00331 $0.00331
Opus 5 $0.00166 $0.00166
Sonnet 5 $0.00066 $0.00066
Haiku 4.5 $0.00033 $0.00033

Measured yesterday against content hash 0c67c0c2360e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 yesterday.

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.

rules/practices/security.mdc · 46 lines

What it actually says

Security Standards (Always Applied)

Non-Negotiable Rules

Secrets

  • NEVER hardcode API keys, passwords, tokens, or credentials
  • NEVER commit .env files with real values
  • Use environment variables or secret managers
  • Rotate any secret accidentally committed

Input Validation

  • Validate ALL external input at system boundaries
  • Use allowlists over denylists
  • Validate type, format, length, range
  • Reject and log invalid input — never silently ignore

SQL/Command Injection

  • Use parameterized queries / prepared statements
  • Never concatenate user input into SQL strings
  • Never pass user input to shell commands (exec, spawn)

Authentication & Authorization

  • Check authorization on EVERY sensitive operation (don't rely on UI hiding)
  • Use established auth libraries — don't roll your own
  • Session tokens: httpOnly, secure, sameSite cookies
  • Implement rate limiting on auth endpoints

Data Handling

  • Encrypt PII at rest and in transit
  • Minimize data collection (only what's needed)
  • Log context, not sensitive data (log userId, not password)

Dependencies

  • Run npm audit / pip audit / cargo audit regularly
  • Fix CRITICAL vulnerabilities immediately
  • Prefer well-maintained packages (recent commits, many maintainers)

When You See a Violation

Flag immediately with: 🔴 SECURITY: {description} at {file}:{line} Do not proceed without addressing it.

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. yesterday First seen · 46 lines · 331 tokens per session scan A 0c67c0c2360e

Subscribe to this mod's changes

security is a cursor rule published in the GitHub repository dasomel/oh-my-cursor (2 stars, last pushed 5mo ago), licensed MIT. It adds 331 tokens to every session, about $0.0017 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 2026-08-31.