fix(security): harden markdown rendering and sync safety

apps/web-app/refresh-skills-plugin.js

@@ -49,6 +49,21 @@ function git(cmd) {
     return execSync(`git ${cmd}`, { cwd: ROOT_DIR, encoding: 'utf-8', stdio: ['pipe', 'pipe', 'pipe'] }).trim();
 }
 
+function isAllowedDevOrigin(req) {
+    const host = req.headers?.host;
+    const origin = req.headers?.origin;
+
+    if (!host || !origin) {
+        return false;
+    }
+
+    try {
+        return new URL(origin).host === host;
+    } catch {
+        return false;
+    }
+}
+
 /** Ensure the upstream remote exists. */
 function ensureUpstream() {
     const remotes = git('remote');
@@ -250,6 +265,19 @@ export default function refreshSkillsPlugin() {
             server.middlewares.use('/api/refresh-skills', async (req, res) => {
                 res.setHeader('Content-Type', 'application/json');
 
+                if (req.method !== 'POST') {
+                    res.statusCode = 405;
+                    res.setHeader('Allow', 'POST');
+                    res.end(JSON.stringify({ success: false, error: 'Method not allowed' }));
+                    return;
+                }
+
+                if (!isAllowedDevOrigin(req)) {
+                    res.statusCode = 403;
+                    res.end(JSON.stringify({ success: false, error: 'Forbidden origin' }));
+                    return;
+                }
+
                 try {
                     let result;
 
@@ -287,3 +315,5 @@ export default function refreshSkillsPlugin() {
         }
     };
 }
+
+export { isAllowedDevOrigin };

apps/web-app/src/__tests__/refresh-skills-plugin.security.test.js

@@ -0,0 +1,98 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const execSync = vi.fn((command) => {
+  if (command === 'git --version') return '';
+  if (command === 'git rev-parse --git-dir') return '.git';
+  if (command === 'git remote') return 'origin\nupstream\n';
+  if (command === 'git rev-parse HEAD') return 'abc123';
+  if (command === 'git fetch upstream main') return '';
+  if (command === 'git rev-parse upstream/main') return 'abc123';
+  return '';
+});
+
+vi.mock('child_process', async (importOriginal) => {
+  const actual = await importOriginal();
+  return {
+    ...actual,
+    execSync,
+    default: {
+      ...actual,
+      execSync,
+    },
+  };
+});
+
+function createResponse() {
+  return {
+    statusCode: 200,
+    headers: {},
+    body: '',
+    setHeader(name, value) {
+      this.headers[name] = value;
+    },
+    end(payload) {
+      this.body = payload;
+    },
+  };
+}
+
+async function loadRefreshHandler() {
+  const { default: refreshSkillsPlugin } = await import('../../refresh-skills-plugin.js');
+  const registrations = [];
+  const server = {
+    middlewares: {
+      use(pathOrHandler, maybeHandler) {
+        if (typeof pathOrHandler === 'string') {
+          registrations.push({ path: pathOrHandler, handler: maybeHandler });
+          return;
+        }
+        registrations.push({ path: null, handler: pathOrHandler });
+      },
+    },
+  };
+
+  refreshSkillsPlugin().configureServer(server);
+  const registration = registrations.find((item) => item.path === '/api/refresh-skills');
+  if (!registration) {
+    throw new Error('refresh-skills handler not registered');
+  }
+  return registration.handler;
+}
+
+describe('refresh-skills plugin security', () => {
+  beforeEach(() => {
+    execSync.mockClear();
+  });
+
+  it('rejects GET requests for the sync endpoint', async () => {
+    const handler = await loadRefreshHandler();
+    const req = {
+      method: 'GET',
+      headers: {
+        host: 'localhost:5173',
+        origin: 'http://localhost:5173',
+      },
+    };
+    const res = createResponse();
+
+    await handler(req, res);
+
+    expect(res.statusCode).toBe(405);
+  });
+
+  it('rejects cross-origin POST requests for the sync endpoint', async () => {
+    const handler = await loadRefreshHandler();
+    const req = {
+      method: 'POST',
+      headers: {
+        host: 'localhost:5173',
+        origin: 'http://evil.test',
+      },
+    };
+    const res = createResponse();
+
+    await handler(req, res);
+
+    expect(res.statusCode).toBe(403);
+  });
+});

apps/web-app/src/pages/Home.tsx

@@ -74,7 +74,7 @@ export function Home(): React.ReactElement {
     setSyncing(true);
     setSyncMsg(null);
     try {
-      const res = await fetch('/api/refresh-skills');
+      const res = await fetch('/api/refresh-skills', { method: 'POST' });
       const data = await res.json();
       if (data.success) {
         if (data.upToDate) {

apps/web-app/src/pages/SkillDetail.tsx

@@ -5,7 +5,6 @@ import { SkillStarButton } from '../components/SkillStarButton';
 import { useSkills } from '../context/SkillContext';
 import remarkGfm from 'remark-gfm';
 import rehypeHighlight from 'rehype-highlight';
-import rehypeRaw from 'rehype-raw';
 
 // Lazy load heavy markdown component
 const Markdown = lazy(() => import('react-markdown'));
@@ -261,7 +260,7 @@ export function SkillDetail(): React.ReactElement {
             <Suspense fallback={<div className="h-24 animate-pulse bg-slate-100 dark:bg-slate-800 rounded-lg"></div>}>
               <Markdown
                 remarkPlugins={[remarkGfm]}
-                rehypePlugins={[rehypeHighlight, rehypeRaw]}
+                rehypePlugins={[rehypeHighlight]}
               >
                 {markdownBody}
               </Markdown>

apps/web-app/src/pages/__tests__/SkillDetail.security.test.tsx

@@ -0,0 +1,69 @@
+import { describe, it, expect, vi, beforeEach, Mock } from 'vitest';
+import { waitFor } from '@testing-library/react';
+import { SkillDetail } from '../SkillDetail';
+import { renderWithRouter } from '../../utils/testUtils';
+import { createMockSkill } from '../../factories/skill';
+import { useSkills } from '../../context/SkillContext';
+
+let capturedRehypePlugins: unknown[] | undefined;
+
+vi.mock('../../components/SkillStarButton', () => ({
+  SkillStarButton: () => <button data-testid="star-button">0 Upvotes</button>,
+}));
+
+vi.mock('../../context/SkillContext', async (importOriginal) => {
+  const actual = await importOriginal<any>();
+  return {
+    ...actual,
+    useSkills: vi.fn(),
+  };
+});
+
+vi.mock('react-markdown', () => ({
+  default: ({ children, rehypePlugins }: { children: string; rehypePlugins?: unknown[] }) => {
+    capturedRehypePlugins = rehypePlugins;
+    return <div data-testid="markdown-content">{children}</div>;
+  },
+}));
+
+describe('SkillDetail security', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    capturedRehypePlugins = undefined;
+  });
+
+  it('does not enable raw HTML rendering for skill markdown', async () => {
+    const mockSkill = createMockSkill({
+      id: 'unsafe-skill',
+      name: 'unsafe-skill',
+      description: 'Skill with embedded html',
+    });
+
+    (useSkills as Mock).mockReturnValue({
+      skills: [mockSkill],
+      stars: {},
+      loading: false,
+    });
+
+    global.fetch = vi.fn().mockResolvedValue({
+      ok: true,
+      text: async () => '# Demo\n\n<img src=x onerror=alert(1) />',
+    });
+
+    renderWithRouter(<SkillDetail />, {
+      route: '/skill/unsafe-skill',
+      path: '/skill/:id',
+      useProvider: false,
+    });
+
+    await waitFor(() => {
+      expect(capturedRehypePlugins).toBeDefined();
+    });
+
+    const pluginNames = (capturedRehypePlugins ?? []).map((plugin) =>
+      typeof plugin === 'function' ? plugin.name : String(plugin),
+    );
+
+    expect(pluginNames).not.toContain('rehypeRaw');
+  });
+});

tools/scripts/generate_index.py

@@ -3,6 +3,7 @@ import json
 import re
 import sys
 from collections.abc import Mapping
+from datetime import date, datetime
 
 import yaml
 from _project_paths import find_repo_root
@@ -13,6 +14,15 @@ if sys.platform == 'win32':
     sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-8')
     sys.stderr = io.TextIOWrapper(sys.stderr.buffer, encoding='utf-8')
 
+def normalize_yaml_value(value):
+    if isinstance(value, Mapping):
+        return {key: normalize_yaml_value(val) for key, val in value.items()}
+    if isinstance(value, list):
+        return [normalize_yaml_value(item) for item in value]
+    if isinstance(value, (date, datetime)):
+        return value.isoformat()
+    return value
+
 def parse_frontmatter(content):
     """
     Parses YAML frontmatter, sanitizing unquoted values containing @.
@@ -43,6 +53,7 @@ def parse_frontmatter(content):
     
     try:
         parsed = yaml.safe_load(sanitized_yaml) or {}
+        parsed = normalize_yaml_value(parsed)
         if not isinstance(parsed, Mapping):
             print("⚠️ YAML frontmatter must be a mapping/object")
             return {}

tools/scripts/tests/test_frontmatter_parsing_security.py

@@ -38,6 +38,31 @@ class FrontmatterParsingSecurityTests(unittest.TestCase):
         self.assertIsNone(metadata)
         self.assertTrue(any("mapping" in error.lower() for error in errors))
 
+    def test_validate_skills_normalizes_unquoted_yaml_dates(self):
+        content = "---\nname: demo\ndescription: ok\ndate_added: 2026-03-15\n---\nbody\n"
+        metadata, errors = validate_skills.parse_frontmatter(content)
+
+        self.assertEqual(errors, [])
+        self.assertEqual(metadata["date_added"], "2026-03-15")
+
+    def test_generate_index_serializes_unquoted_yaml_dates(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            root = Path(temp_dir)
+            skills_dir = root / "skills"
+            skill_dir = skills_dir / "demo"
+            output_file = root / "skills_index.json"
+
+            skill_dir.mkdir(parents=True)
+            (skill_dir / "SKILL.md").write_text(
+                "---\nname: demo\ndescription: ok\ndate_added: 2026-03-15\n---\nBody\n",
+                encoding="utf-8",
+            )
+
+            skills = generate_index.generate_index(str(skills_dir), str(output_file))
+
+            self.assertEqual(skills[0]["date_added"], "2026-03-15")
+            self.assertIn('"date_added": "2026-03-15"', output_file.read_text(encoding="utf-8"))
+
     def test_generate_index_ignores_symlinked_skill_markdown(self):
         with tempfile.TemporaryDirectory() as temp_dir:
             root = Path(temp_dir)

tools/scripts/validate_skills.py

@@ -5,6 +5,7 @@ import sys
 import io
 import yaml
 from collections.abc import Mapping
+from datetime import date, datetime
 from _project_paths import find_repo_root
 
 
@@ -38,6 +39,15 @@ WHEN_TO_USE_PATTERNS = [
 def has_when_to_use_section(content):
     return any(pattern.search(content) for pattern in WHEN_TO_USE_PATTERNS)
 
+def normalize_yaml_value(value):
+    if isinstance(value, Mapping):
+        return {key: normalize_yaml_value(val) for key, val in value.items()}
+    if isinstance(value, list):
+        return [normalize_yaml_value(item) for item in value]
+    if isinstance(value, (date, datetime)):
+        return value.isoformat()
+    return value
+
 def parse_frontmatter(content, rel_path=None):
     """
     Parse frontmatter using PyYAML for robustness.
@@ -51,6 +61,7 @@ def parse_frontmatter(content, rel_path=None):
     fm_errors = []
     try:
         metadata = yaml.safe_load(fm_text) or {}
+        metadata = normalize_yaml_value(metadata)
         if not isinstance(metadata, Mapping):
             return None, ["Frontmatter must be a YAML mapping/object."]