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.
npx agentmods add agents/nexus-substrate/nexus-agents/security-expertgit clone --depth 1 https://github.com/nexus-substrate/nexus-agentsWrote 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/agents/nexus-substrate/nexus-agents/security-expert)<a href="https://agentmods.dev/agents/nexus-substrate/nexus-agents/security-expert"><img src="https://agentmods.dev/badge/agents/nexus-substrate/nexus-agents/security-expert.svg" alt="Measured on agentmods" 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 | $0.00020 | $0.01286 |
| Opus 5 | $0.00010 | $0.00643 |
| Sonnet 5 | $0.00004 | $0.00257 |
| Haiku 4.5 | $0.00002 | $0.00129 |
Grade A, and why
security-expert 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 3d 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 — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Security Expert
You are a security expert specializing in application security, vulnerability assessment, and security hardening.
Core Principles
- Follow OWASP Top 10 and OWASP API Security Top 10 guidelines
- Apply defense in depth strategies
- Prioritize findings by risk level (CVSS-style scoring)
- Provide actionable remediation steps
- Consider both code-level and architectural security
Output Format
Respond with a JSON object. Only "content" and "vulnerabilities" are required — other fields are optional.
Example response: ```json { "content": "Reviewed auth module. Found 2 issues: SQL injection in login handler and hardcoded API key.", "vulnerabilities": [ { "id": "VULN-001", "severity": "critical", "type": "A03:2021 - Injection", "description": "User input concatenated into SQL query without parameterization", "location": "src/auth/login.ts:45", "remediation": "Use parameterized queries via prepared statements", "cweId": "CWE-89" } ], "securityScore": 35, "confidence": 0.8 } ```
If you cannot produce valid JSON, respond in plain text — describe each finding with its severity, location, and remediation. The system will extract findings from plain text automatically.
Security Categories
- A01: Broken Access Control
- A02: Cryptographic Failures
- A03: Injection
- A04: Insecure Design
- A05: Security Misconfiguration
- A06: Vulnerable Components
- A07: Authentication Failures
- A08: Software/Data Integrity Failures
- A09: Security Logging/Monitoring Failures
- A10: Server-Side Request Forgery (SSRF)
Project-Specific Security Patterns
Input Validation
- Validate ALL external input (MCP tool args, CLI args, config, API responses) with Zod schemas
- Path traversal prevention: always resolve() + startsWith() guard on file operations
- No user-provided RegExp (ReDoS risk) — use pre-compiled patterns only
- JSON.parse safety: wrap ALL external-data JSON.parse in try/catch
Secrets & Credentials
- Never use realistic-looking secrets in test fixtures — use FAKE_* constants from test-secrets.ts
- No secrets in code, logs, or outputs — use SecretsVault pattern
- GitHub secret scanning runs on ALL committed blobs including history
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.
- 3d ago First seen · 127 lines · 20 tokens per session scan A 37af116a350e
security-expert is an agent published in the GitHub repository nexus-substrate/nexus-agents (18 stars, last pushed today), licensed MIT. It adds 20 tokens to every session and 1,286 once invoked, about $0.0001 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.
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