# GSD Core security model > **Explanation** — This document describes *why* GSD Core has the security > posture it does and *how the layers fit together*. It is not a reference for > every hook parameter. For the `/gsd-secure-phase` command and its options, > see [Commands](../COMMANDS.md). For the implementation-level hook > architecture, see [Architecture § Hook System](../ARCHITECTURE.md#hook-system). > For the org-wide security baseline (scanner controls, incident checklists, > ownership model), see [SECURITY.md](../../SECURITY.md). --- ## Why AI-driven development needs a dedicated security posture A conventional code editor does not execute arbitrary packages on your behalf. GSD Core does. The research → plan → execute pipeline automates the full path from "name a package" to "run `npm install `", from "write a planning artifact" to "use that artifact as an LLM system prompt". Each automation step removes a human from the loop — and each removal is a potential attack surface. GSD Core's security model is built around one organising principle: **defence in depth**. No single control is assumed to be perfect. Several overlapping layers each reduce a distinct class of risk, and together they make the attack surface substantially harder to exploit without eliminating it entirely. The honest summary at the end of this document explains what the system cannot protect against. --- ## Layer 1 — Supply-chain protection: the Package Legitimacy Gate ### The threat AI models hallucinate package names. This is not a fringe failure mode: 2025 research documents roughly 20 % of AI-generated package references as hallucinated names that do not correspond to legitimate packages. A subset of those hallucinated names — approximately 43 % in the same research — recur consistently across prompts, meaning an attacker can observe which names AI tools commonly produce and pre-register those names on npm, PyPI, or crates.io with malicious post-install scripts. The technique is called *slopsquatting*. The insidious quality of slopsquatting is that a hallucinated name that passes `npm view` *looks legitimate*. The registry entry proves only that someone registered the name — not that the package does what the AI said it does, not that it has any legitimate users, and not that its install scripts are safe. Without a gate, a hallucinated name would flow undetected through GSD's researcher → planner → executor pipeline and eventually run as `npm install ` on your machine. ### How the gate works The gate operates across three pipeline stages: **Research stage.** When `gsd-phase-researcher` recommends external packages, it runs `gsd-tools query package-legitimacy check --ecosystem ` against each one. Verdicts (`OK|SUS|SLOP`) are computed from live registry APIs against thresholds `{ minAgeDays: 30, minWeeklyDownloads: 1000, requireRepo: true }`, plus terminal short-circuits for non-existence and suspicious `postinstall` scripts. The results are written to a `## Package Legitimacy Audit` table in `RESEARCH.md`. Packages tagged `[SLOP]` (high-confidence hallucination or attacker-registered) are **stripped from `RESEARCH.md` entirely** before the file is saved. They never reach the planner. **Planning stage.** `gsd-planner` reads the Audit table. For any package tagged `[SUS]` (suspicious: newly registered, low download count, no source repository, or naming pattern close to a popular package) or `[ASSUMED]` (sourced from WebSearch rather than direct registry verification), the planner **inserts a `checkpoint:human-verify` task** before the install step. The checkpoint includes a direct link to the registry page and specific things to look for: maintainer history, issue-tracker activity, absence of suspicious install scripts. **Execution stage.** If an install fails, `gsd-executor` **surfaces a checkpoint and stops**. It does not silently try an alternative package name — which could itself be malicious. This is an explicit rule in the executor's behaviour (RULE 3 in the executor agent definition). ### Why WebSearch packages are always `[ASSUMED]` Package names discovered through WebSearch are tagged `[ASSUMED]` regardless of whether `npm view` succeeds. A package that exists on the registry is not the same as a package that is safe to install. `npm view` proves registration, not legitimacy. The `[ASSUMED]` tag triggers the same human-verify checkpoint as `[SUS]`, ensuring that any unverified web-discovered recommendation always gets a human review before installation. ### Ecosystem coverage The gate resolves signals directly from each ecosystem's registry API rather than a single generic check: - Node.js: `registry.npmjs.org` (age, repository URL, `postinstall` script) plus `api.npmjs.org/downloads` (weekly downloads) - Python: `pypi.org/pypi//json` (age, repository URL) - Rust: the crates.io API (age, weekly downloads, repository URL) This covers cross-ecosystem hallucination, which occurs at roughly 9 % according to 2025 USENIX research — cases where an AI recommends a package that exists in one ecosystem but not the one actually in use. ### Graceful degradation Each registry adapter has a 5-second timeout and returns degraded (all-null) signals on a failed lookup rather than throwing. Missing signals surface as `unknown-age` / `unknown-downloads` reasons, which push a package to `[SUS]` — and `[SUS]` is gated behind the same `checkpoint:human-verify` task as `[ASSUMED]`. The gate fails toward human review, not silence, and research and planning proceed normally: nothing here hard-fails on a network or tool outage. `slopcheck` is an optional adapter that can only escalate a verdict, never lower it, and is not the install-or-degrade gate. No shipped configuration wires it; its absence leaves registry-API verdicts intact rather than downgrading everything to `[ASSUMED]`. --- ## Layer 2 — Prompt injection defences ### The threat GSD Core generates Markdown files that become LLM system prompts. The research pipeline reads external web content; the planning pipeline incorporates user-supplied text (`--text-file`, `--prd`); the execution pipeline writes planning artifacts that are later re-read as agent context. Any user-controlled text flowing into these artifacts is a potential **indirect prompt injection** vector — an attacker-controlled string that, once inside a system prompt, attempts to override the agent's instructions or exfiltrate information. ### How the defences work GSD Core addresses prompt injection at three levels. **Input validation (`security.cjs`).** The `gsd-core/bin/lib/security.cjs` module is the central security utility. It provides: - Path traversal prevention: user-supplied file paths (`--text-file`, `--prd`) are validated to resolve within the project directory, with macOS `/var` → `/private/var` symlink resolution handled explicitly - Prompt injection detection: known injection patterns (role overrides, instruction bypasses, system tag injections) are scanned in user-supplied text before it enters any planning artifact - Safe JSON parsing: a wrapper that prevents prototype-pollution attacks via crafted JSON payloads - Shell argument validation: arguments passed to subshell commands are validated before use **Runtime hook: `gsd-prompt-guard.js`.** This hook fires on every Write or Edit call that targets `.planning/` files. It scans the content being written for the same injection patterns as `security.cjs` (a subset inlined directly into the hook for independence — the hook does not `require()` the module, so it runs even if the module path changes). Detection is **advisory-only**: the hook logs the finding but does not block the write. The rationale is that a false-positive block on a legitimate planning write would be more disruptive than a missed injection in a secondary scan layer. **Runtime hook: `gsd-read-injection-scanner.js`.** This hook fires on the output of every Read, WebFetch, and WebSearch tool call. It scans the *content that was just read or fetched* for injected instructions in untrusted content — catching cases where an attacker has embedded instructions in a file or remote resource that GSD is about to incorporate into an agent's context. The 10 research and doc-ingest agents additionally carry a shared `` data/instruction boundary (defined in `gsd-core/references/untrusted-input-boundary.md`): `gsd-project-researcher`, `gsd-phase-researcher`, `gsd-ui-researcher`, `gsd-assumptions-analyzer`, `gsd-advisor-researcher`, `gsd-doc-classifier`, `gsd-doc-synthesizer`, `gsd-research-synthesizer`, `gsd-ai-researcher`, and `gsd-domain-researcher`. Any content fetched or read by those agents is treated as data, never as instructions, regardless of what the content claims to be. **Opt-in blocking (`security.injection_blocking`).** By default all injection detections are advisory-only (logged, not blocked). Setting `security.injection_blocking = true` in `.planning/config.json` (a registered config key — `gsd config-set security.injection_blocking true`) upgrades HIGH-confidence detections to **blocking**. Be precise about what this does: the scanner is a **PostToolUse** hook, so it runs *after* the Read/WebFetch/WebSearch has already executed and the fetched content is already in the model's transcript. Blocking does **not** retroactively redact that content — it emits `decision: "block"`, which halts the agent's next step and feeds the detection back as the reason, so the agent is stopped from acting further on the flagged result instead of silently continuing. LOW detections remain advisory under this setting. This flag is opt-in; the default (advisory-only) is preserved to avoid breaking existing workflows. The prompt-level boundary above (treat fetched text as data, never instructions) is the layer that keeps an injection from being *followed* even while it sits in context; the hook is a coarse pattern pre-filter and circuit-breaker, not a redactor. **CI scanner.** `prompt-injection-scan.security.test.cjs` scans all agent, workflow, and command files for embedded injection vectors as part of the test suite. This catches injection attempts in the GSD source itself — for example, a supply-chain attack that modified a workflow file to add a role-override instruction. ### Read Injection Scanner vs Prompt Guard The two hooks cover complementary surfaces. `gsd-prompt-guard.js` watches *writes to planning artifacts* — it catches injection being planted. `gsd-read-injection-scanner.js` watches *reads and remote fetches* — it catches injection being ingested from external content (a dependency's README, a third-party config file, a user-provided document, or any URL fetched via WebFetch or WebSearch). The in-prompt `` boundary in research agents provides an additional containment layer: even if an injected string reaches an agent, it is structurally separated from the instruction region. Together these controls bracket the ingest → store → re-read lifecycle. --- ## Layer 3 — Repository and dependency integrity Upstream of GSD's runtime behaviour, the `open-gsd` organisation enforces controls at the repository and package level. These are documented in full in [`docs/security/baseline.md`](../security/baseline.md) and are summarised here for completeness. **Dependency integrity.** All third-party dependencies are pinned via `package-lock.json` and verified against published checksums before install. A `scripts/check-npm-integrity.cjs` gate detects invalid versions, missing packages, and extraneous packages at CI time. This mitigates dependency confusion and typosquatting attacks against GSD's own dependencies. **Secret scanning.** Every commit and PR is scanned for hardcoded secrets. Intentional test fixtures must be annotated with the project-standard exclusion grammar (see `SECURITY.md` for the annotation format). Un-annotated suppressions fail CI. **Locale-safe text scanning.** Output and user-facing strings are scanned for Unicode homoglyphs, bidirectional override characters, and invisible Unicode — the class of attacks documented in CVE-2021-42574 ("Trojan Source") that can hide malicious content in diffs. --- ## Trade-offs and limits The security model described here meaningfully reduces the attack surface for AI-driven development. It does not eliminate supply-chain risk. **What the Package Legitimacy Gate reduces:** The probability that a hallucinated or attacker-registered package reaches `npm install` without a human checkpoint. The `[SLOP]` gate removes high-confidence bad packages entirely; the `[SUS]` / `[ASSUMED]` gates require human review before execution. This substantially raises the cost of a successful slopsquatting attack. **What the Package Legitimacy Gate does not eliminate:** A legitimate package that is later compromised (account takeover, dependency confusion in its own tree) is not caught by the registry-API gate, which checks registration signals at research time. Lock files and `npm audit` at the dependency-integrity layer are the controls for that class of attack. **What the prompt injection defences reduce:** The probability that user-controlled text in planning artifacts successfully overrides agent instructions. Pattern-matching on known injection forms catches the common cases; novel jailbreaks or low-signal injections may pass undetected. The advisory-only posture means detection is logged but not blocked — a deliberate choice that preserves workflow continuity at the cost of not hard-stopping on a detection. **What the prompt injection defences do not eliminate:** A sufficiently creative injection that does not match known patterns, or an injection that arrives through a channel the hooks do not cover. The previously uncovered channel of content injected into a dependency's published README and read by a subagent browsing documentation is now scanned at ingress by `gsd-read-injection-scanner.js` (which covers WebFetch and WebSearch output) and structurally isolated in-prompt by the `` boundary in research agents — but novel jailbreaks and low-signal injections may still pass undetected. Defence in depth means each layer makes the attack harder, not that any single layer makes it impossible. **Reporting vulnerabilities.** Report via private GitHub security advisory at `https://github.com/open-gsd/gsd-core/security/advisories/new`. Do not open public issues. See [SECURITY.md](../../SECURITY.md) for the response timeline and disclosure policy. --- ## Related - [Commands](../COMMANDS.md) — includes `/gsd-secure-phase` and `/gsd-code-review` with security-relevant flags - [Architecture § Hook System](../ARCHITECTURE.md#hook-system) — implementation detail on every hook, its event trigger, and safety properties - [SECURITY.md](../../SECURITY.md) — vulnerability reporting, org-wide security baseline, secret-scan exclusion governance, and dependency integrity verification - [Docs index](../README.md)