brin-security

A set of security rules for checking external dependencies and web content with the brin API before installing, using, or trusting them.

In plain words
What is it for?
Use it when evaluating packages, online material, or other external dependencies before allowing them into your workflow.
Why use it?
It adds a security review step when your project depends on code or content from outside sources.

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/superagent-ai/brin/brin-security
Clone the repo
git clone --depth 1 https://github.com/superagent-ai/brin
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 907 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin unknown 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 $0.00000 $0.00907
Opus 5 $0.00000 $0.00453
Sonnet 5 $0.00000 $0.00181
Haiku 4.5 $0.00000 $0.00091

Measured 2d ago against content hash a5cf32ff4599, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

brin-security scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

2. **Before fetching a URL**: If using `curl`, `wget`, or any HTTP client to retrieve web content, the domain is automatically checked by the pre-shell hook. For programmatic fetches, check the domain first.
plugins/cursor/rules/brin-security.mdc · 108 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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 · 108 lines · 0 tokens per session scan A a5cf32ff4599

Subscribe to this mod's changes

brin-security is a cursor rule published in the GitHub repository superagent-ai/brin (50 stars, last pushed 5mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 907 tokens. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.