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-c)<a href="https://agentmods.dev/rules/matank001/cursor-security-rules/secure-dev-c"><img src="https://agentmods.dev/badge/rules/matank001/cursor-security-rules/secure-dev-c/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-c"><img src="https://agentmods.dev/badge/rules/matank001/cursor-security-rules/secure-dev-c.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 | $0.00497 |
| Opus 5.5 | $0.00000 | $0.00199 |
| Sonnet 5.5 | $0.00000 | $0.00099 |
| Haiku 4.5 | $0.00000 | $0.00050 |
Grade A, and why
secure-dev-c 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- security-lang-c — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Secure C Development
These rules apply to all C source and header files in the repository and aim to prevent memory corruption, code injection, and unsafe system behavior.
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 Unsafe Functions
- Rule: Do not use functions like
gets,strcpy,sprintf, orscanfwith%s. Use bounded or safer alternatives likefgets,strncpy, orsnprintf.
2. Always Validate Input Lengths
- Rule: Validate the length of user or external input before copying, storing, or processing it to prevent buffer overflows.
3. Initialize All Pointers and Memory
- Rule: All pointers and allocated memory must be explicitly initialized before use.
4. Check All Memory Allocations
- Rule: Check the result of
malloc,calloc, orreallocforNULLbefore using the returned pointer.
5. Avoid Format String Vulnerabilities
- Rule: Never pass user-controlled strings directly as the format argument to functions like
printf,fprintf, orsyslog.
6. Free All Allocated Memory
- Rule: All dynamic memory must be properly freed to avoid memory leaks. Avoid double-free and use-after-free errors.
7. Do Not Trust Environment Variables
- Rule: Environment variables must not be used directly in sensitive operations like file access, exec calls, or security checks without validation.
8. Avoid System and Shell Calls with Input
- Rule: Do not use
system(),popen(), or similar functions with user-controlled input. Use direct APIs when possible.
9. Limit Pointer Arithmetic and Casting
- Rule: Avoid unnecessary pointer arithmetic and type casting that can bypass bounds or type safety.
10. Use Static Analysis and Compiler Warnings
- Rule: Enable strict compiler warnings (
-Wall -Wextra -Werror) and use static analysis tools (e.g.,clang-tidy,cppcheck) to detect risky patterns.
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 · 43 lines · 497 tokens per session scan A 96c7a93ca810
secure-dev-c is a cursor rule published in the GitHub repository matank001/cursor-security-rules (381 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 497 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.
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