security

A set of security rules for code that handles data, login, permissions, or outside systems. It covers validating input, safely producing output, and managing authentication-related data.

In plain words
What is it for?
Use it when building or reviewing web applications, servers, APIs, file uploads, database queries, or authentication flows.
Why use it?
It helps reduce common risks such as SQL injection, cross-site scripting, command injection, and unsafe handling of untrusted data.

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/e-gov/cursor-prompts/security
Clone the repo
git clone --depth 1 https://github.com/e-gov/cursor-prompts
Per session 2,812 This file is loaded in full into every session.
When invoked 2,812 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 $0.02812 $0.02812
Opus 5 $0.01406 $0.01406
Sonnet 5 $0.00562 $0.00562
Haiku 4.5 $0.00281 $0.00281

Measured 2d ago against content hash e4cefbfe6150, 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 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.

rules/common/security.mdc · 272 lines

How it starts

The opening of the file, as written. The whole thing — 272 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Comprehensive Security Best Practices

Context

  • Apply when writing or reviewing any code that handles data, authentication, authorization, or external interactions
  • These rules cover both general, language-agnostic principles and specific requirements for web applications/servers
  • Based on industry standards including OWASP ASVS and security best practices

Requirements

Input Validation and Output Handling

  • Input Validation:
    • Sanitize and validate all external input (user input, API requests, file uploads, environment variables) to prevent injection attacks (SQLi, XSS, XXE, command injection)
    • Use allow-lists for validation rather than block-lists where possible
    • Data selection/database queries must use parameterized queries, ORMs, or equivalent protections
    • Protect against OS command injection using parameterized queries or contextual command line output encoding
    • All untrusted HTML input from WYSIWYG editors must be sanitized using a secure library
    • Avoid eval() or dynamic code execution; if unavoidable, sanitize user input before execution
    • Input must be decoded/unescaped into canonical form only once before processing
  • Output Encoding:
    • Encode output appropriately for its context (HTML, JavaScript, SQL, logs) to prevent XSS and other injection issues
    • Use proper Content-Type header field that matches the actual content
    • Output encoding must be performed as a final step before interpreter use

Authentication and Password Management

  • Password Requirements:
    • User-set passwords must be at least 8 characters (15+ recommended), up to 64 characters permitted
    • Check passwords against known-breached password lists using a k-anonymity API (e.g., HIBP) or equivalent service; do not rely on fixed-size “top-N” lists
    • Allow passwords of any composition; no forced complexity requirements
    • Password input fields must use type=password; allow paste functionality and password managers
    • Verify passwords exactly as received (no truncation or case transformation)
  • Authentication Mechanisms:
    • Use strong, standard authentication mechanisms with multi-factor authentication
    • Implement rate limiting and anti-automation controls against credential stuffing and brute force
    • Default accounts (root, admin, sa) must be disabled or removed
    • System-generated passwords must be securely random and expire after short use
    • No password hints or knowledge-based authentication ("secret questions")
    • Users must be able to change passwords with current password verification

Read the full file on GitHub · 272 lines

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. 2d ago First seen · 272 lines · 2,812 tokens per session scan A e4cefbfe6150

Subscribe to this mod's changes

security is a cursor rule published in the GitHub repository e-gov/cursor-prompts (34 stars, last pushed 4mo ago), licensed MIT. It adds 2,812 tokens to every session, about $0.0141 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.