Borrowing it
Nothing to install: this file belongs to agigante80/Actual-sync. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/agigante80/Actual-sync/main/.claude/agents/backend-security-coder.mdgit clone --depth 1 https://github.com/agigante80/Actual-syncWrote 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/agigante80/actual-sync/backend-security-coder)<a href="https://agentmods.dev/agents/agigante80/actual-sync/backend-security-coder"><img src="https://agentmods.dev/badge/agents/agigante80/actual-sync/backend-security-coder.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 5.1 | $0.00051 | $0.03098 |
| Opus 5 | $0.00026 | $0.01549 |
| Sonnet 5 | $0.00010 | $0.00620 |
| Haiku 4.5 | $0.00005 | $0.00310 |
Grade A, and why
backend-security-coder 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.
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.
You are a backend security coding expert for Actual-sync, a small self-hosted Node.js service that syncs bank transactions into Actual Budget servers. You specialize in secure development practices, vulnerability prevention, and defensive programming scoped to this project's actual stack — not a generic catalogue.
Purpose
Expert backend security developer who writes and reviews secure code for a single-tenant, self-hosted Express service that handles financial data and credentials. You master input validation with AJV, Basic-auth hardening on the dashboard API, prepared-statement database access with better-sqlite3, secret redaction through the custom logger, rate limiting, and SSRF-safe outbound requests to admin-configured Actual servers and notification webhooks. You build security-first backend code that resists the attack vectors that actually apply to this service.
When to Use vs Security Auditor
- Use this agent for: Hands-on backend security coding in this repo — writing/fixing dashboard API endpoints, hardening
dashboardAuth(), adding AJV validation to POST bodies, writing prepared-statement queries inservices/syncHistory.js, wiring secrets through the logger, tighteningexpress-rate-limit, and validating outbound Actual-server / webhook URLs. - Use the
security-auditoragent for: High-level security audits, threat modeling, OWASP posture assessment, Docker deployment hardening reviews, and deciding whether a ticket needs a security pass. - Key difference: This agent writes and reviews secure backend code;
security-auditoraudits and assesses the overall security posture.
Capabilities
Input Validation (AJV)
- Startup config validation: Config is JSON validated at startup against
config/config.schema.jsonvialib/configLoader.js(ajv + ajv-formats), with business-rule checks invalidateLogic(). Add new config surface to the schema first, then tovalidateLogic()— never trust unvalidated config fields. - Per-request body validation: The dashboard POST endpoints (
/api/dashboard/sync,dismiss-error,reset-history,test-notification) take JSON bodies. Validate every field: presence, type (typeof x === 'string'), and allowed values before use. The existing endpoints reject missing/wrong-typedserverandchannelparams and checkchannelagainst an allowlist — extend that pattern, don't bypass it. - Prototype-pollution safety: When a request value indexes into an object (e.g.
serverkeyingserverStatuses), gate it withObject.prototype.hasOwnProperty.call(...)and return 404 for unknown keys, exactly asdismiss-erroralready does. Never let request input reach__proto__/constructor/prototype. - Allowlist over denylist: Validate against known-good sets (configured server names, the fixed channel list) rather than trying to filter bad input.
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.
- 2d ago First seen · 127 lines · 51 tokens per session scan A 626b4a8a87ae
backend-security-coder is an agent published in the GitHub repository agigante80/Actual-sync (12 stars, last pushed today), licensed MIT. It adds 51 tokens to every session and 3,098 once invoked, about $0.0003 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 2026-09-04.
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