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.
git clone --depth 1 https://github.com/matank001/cursor-security-rulesWrote 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.
[](https://agentmods.dev/rules/matank001/cursor-security-rules/secure-dev-ruby)<a href="https://agentmods.dev/rules/matank001/cursor-security-rules/secure-dev-ruby"><img src="https://agentmods.dev/badge/rules/matank001/cursor-security-rules/secure-dev-ruby/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.
<a href="https://agentmods.dev/rules/matank001/cursor-security-rules/secure-dev-ruby"><img src="https://agentmods.dev/badge/rules/matank001/cursor-security-rules/secure-dev-ruby.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00000 | $0.00607 |
| Opus 5.5 | $0.00000 | $0.00243 |
| Sonnet 5.5 | $0.00000 | $0.00121 |
| Haiku 4.5 | $0.00000 | $0.00061 |
Grade A, and why
secure-dev-ruby 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Secure Ruby Development
These rules apply to all Ruby code in the repository (including Rails apps, scripts, and gems) and aim to prevent common security vulnerabilities through safe coding patterns, input validation, and proper use of the Ruby standard library.
All violations must include a clear explanation of which rule was triggered and why, to help developers understand and fix the issue effectively.
Generated code must not violate these rules. If a rule is violated, a comment must be added explaining the issue and suggesting a correction.
1. Avoid eval, exec, and Back-Ticks With User Input
- Rule: Do not use
eval,exec,%x{}, or back-ticks with user-controlled data. Use safe APIs (Open3.capture2e, etc.) and parameterization instead.
2. Use Parameterized Database Queries
- Rule: Never build SQL by string interpolation. Use ActiveRecord placeholders (
where("username = ?", user_input)) or prepared statements. - Unsafe:
User.where("username = '#{params[:username]}'") - Safe:
User.where("username = ?", params[:username])
3. Validate and Sanitize All Input
- Rule: Validate type, length, and format of all external input. In Rails, use Strong Parameters and allow-lists.
4. Use Safe YAML Loading
- Rule: Use
YAML.safe_load(orPsych.safe_load) for parsing YAML. Never callYAML.loadon untrusted input.
5. Do Not Deserialize Untrusted Data
- Rule: Avoid
Marshal.load,JSON.parsewithobject_class, or similar deserialization on untrusted sources.
6. Avoid Unsafe File Operations
- Rule: Do not call
File.open,Dir.glob, orsend_filewith raw user input. Sanitize paths and enforce allow-lists.
7. Protect Secrets and Credentials
- Rule: Do not hard-code secrets in source. Use
Rails.credentials, ENV vars, or secret managers. Do not log sensitive data.
8. Use Constant-Time Comparison for Secrets
- Rule: Use
ActiveSupport::SecurityUtils.secure_compare(or Rack equivalent) when comparing tokens or signatures.
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.
- 1mo ago First seen · 51 lines · 607 tokens per session scan A a44176b50931
secure-dev-ruby is a cursor rule published in the GitHub repository matank001/cursor-security-rules (382 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 607 tokens. 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.
Other cursor rules, from other repositories
dragonruby-best-practices-cursorrules-prompt-file
Cursor rules for DragonRuby development with best practices integration.
rails
Rails: thin controllers, service objects, Turbo.
ruby
Idiomatic Ruby: blocks, RSpec, clean patterns.
dragonruby-general-ruby-rules
description: Applies general Ruby coding style, structure, and best practices for DragonRuby projects. globs: /.rb.
dragonruby-syntax-and-formatting
description: Dictates syntax and formatting guidelines for Ruby code within DragonRuby projects, adhering to the Ruby Style Guide. globs: /.rb.
dragonruby-error-handling
description: Defines error handling and validation strategies within Ruby code in DragonRuby projects. globs: /.rb.