# Threat Model Execution Transcript

## Task Understanding

I was asked to perform a security threat model analysis of the `dev-rfc` skill located at `skills/.experimental/dev-rfc/`. This skill generates an HTML review page for RFC documents, with a particular focus on the review template at `assets/review_template.html` that renders user-submitted RFC markdown and displays it in the browser. The analysis was to follow the threat-model skill's methodology and output format exactly.

## Steps Taken

### Step 1: Read the threat-model skill's guidance

**Why:** The skill's SKILL.md and referenced files define the methodology, output format, and attack patterns to apply.

**Tools used:** Read tool on four files:
- `skills/.experimental/threat-model/SKILL.md` -- workflow overview and key principles
- `skills/.experimental/threat-model/references/methodology.md` -- seven-phase methodology (survey, component mapping, assets, trust boundaries, attack surfaces, calibration, output)
- `skills/.experimental/threat-model/references/output-format.md` -- exact four-section document structure with templates
- `skills/.experimental/threat-model/references/attack-patterns.md` -- technology-specific patterns to check (CLI, web/HTML, injection, dependencies, etc.)

### Step 2: Codebase survey of the dev-rfc skill

**Why:** Phase 1 of the methodology requires understanding what the project is, how it's deployed, and what its primary security concerns are.

**Tools used:**
- Bash `ls` to list the skill's directory structure
- Glob to find all files in the skill
- Read on `SKILL.md`, `references/template.md`, `package.json`, `bun.lock`

**Findings:** The skill has three runtime modes (server, live, static), uses Bun as the runtime, has a single dependency (`open@^10.1.0` for browser launching), and includes vendored copies of `marked.min.js` and `mermaid.min.js` as CDN fallbacks.

### Step 3: Deep analysis of the server script

**Why:** Phase 2 (component mapping) and Phase 4 (trust boundaries) require understanding data flows and input handling.

**Tools used:** Read on `scripts/generate_review.ts` (full file, 875 lines)

**Key findings:**
- `buildHtml()` function performs string replacement of `__DOC_TITLE__` with only `"` -> `&quot;` escaping (no `<>` escaping)
- `__MARKDOWN_CONTENT__` is injected via `JSON.stringify()` which doesn't escape `</script>` sequences
- `killPort()` uses `execSync` with template literal interpolation (mitigated by `parseInt`)
- Server binds to `127.0.0.1` only
- No CORS headers or authentication on any endpoint
- Asset serving has path traversal protection (checks for `/`, `\`, `..` in filename)
- Static mode writes to predictable `/tmp/` path

### Step 4: Deep analysis of the HTML template

**Why:** The template is where markdown is rendered to HTML and where the primary XSS attack surface lives.

**Tools used:**
- Read on `assets/review_template.html` in multiple ranges (lines 1-200, 200-400, 835-900, 890-1060, 1100-1180, 1260-1300, 1400-1600, 1600-1800)
- Grep for `innerHTML`, `outerHTML`, `marked`, `escapeHtml`, `textContent`, `sanitize`, `DOMPurify`
- Grep for `__MARKDOWN_CONTENT__`, `__DOC_TITLE__` and other template variables
- Grep for `eval`, `Function`, `document.write`
- Grep for `marked.parse`, `marked.setOptions`, `marked.use`

**Key findings:**
- `marked.parse()` is called at three locations (lines 917, 1510, 1700) with output assigned to `innerHTML` without any sanitization
- No DOMPurify or equivalent HTML sanitizer is used anywhere
- `escapeHtml()` is implemented (lines 1416-1419) and used for user feedback text and headings in some paths, but NOT for `marked.parse()` output
- Batch mode line 998 injects `sec.heading` (from `textContent`, incidentally safe) but `sec.html` (line 999) is raw unsanitized HTML
- Live mode correctly uses `escapeHtml()` for headings but injects `rendered` (unsanitized marked output) at lines 1514 and 1705
- CDN scripts loaded without SRI from jsdelivr and esm.sh

### Step 5: Analysis of the Python equivalent and test file

**Why:** Cross-referencing to confirm patterns and check for additional attack surfaces.

**Tools used:** Read on `scripts/generate_review.py` (first 100 lines), Read on `scripts/generate_review.test.ts` (full file)

**Findings:** The Python version has identical `__DOC_TITLE__` escaping (only `"` -> `&quot;`). The test file includes a path traversal test (confirming awareness of the issue) but no XSS tests.

### Step 6: Attack surface enumeration and calibration

**Why:** Phases 5 and 6 of the methodology -- the core of the threat model.

**Approach:** Mapped each attacker-controlled input to the data operations performed on it, using the risk class table from the methodology. Identified nine distinct attack surfaces grouped by functional area. Calibrated severity based on the localhost deployment context, with scope notes for elevated-risk scenarios (static/file:// mode, shared machines, concurrent browsing).

### Step 7: Output generation

**Why:** Phase 7 -- write the structured THREAT-MODEL.md following the exact output format.

**Tools used:** Write tool to create `THREAT-MODEL.md` in the specified output directory.

## Issues Encountered

1. **Large HTML template:** The `review_template.html` file (56KB, ~1800 lines) exceeded the 10,000-token read limit. Resolved by reading in multiple offset/limit ranges and using Grep to find specific patterns.

2. **No issues with methodology application:** The skill's methodology was straightforward to follow. The attack patterns reference for "Web & HTML Generation" (XSS in generated HTML, `marked.parse()` without sanitizer) directly matched the primary finding.

## Output Produced

- **`THREAT-MODEL.md`** at `/Users/pedroproenca/Documents/Projects/dot-skills/skills/.experimental/threat-model-workspace/iteration-1/eval-1-dev-rfc-review-ui/with_skill/run-1/outputs/THREAT-MODEL.md`

The document follows the four-section structure:
1. **Overview** -- system description, deployment model, security goals
2. **Threat model, Trust boundaries and assumptions** -- assets, input classification (attacker/operator/developer-controlled), scope assumptions
3. **Attack surface, mitigations and attacker stories** -- nine subsections (3.1-3.9) covering XSS via marked.parse(), title injection, heading injection, CDN supply chain, CSRF, temp file predictability, shell command patterns, workspace path issues, and feedback pollution, plus an out-of-scope section
4. **Criticality calibration** -- 0 Critical, 2 High, 4 Medium, 3 Low findings with scope notes
