Fix npm security advisories

.github/scripts/fix-advisories.js

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+// Fixes the npm advisories Dependabot reports as "No update possible": a transitive package held
+// back by an exact pin in `overrides` or by its parent's version range. Dependabot never edits
+// `overrides`, so this script does. Run by workflows/security-auto-fix.yml from the repo root.
+import { execFileSync, spawnSync } from 'node:child_process';
+import { appendFileSync, readFileSync, writeFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+const PACKAGES = ['front-end', 'back-end'];
+
+const npm = (cwd, ...args) => execFileSync('npm', args, { cwd, encoding: 'utf8', stdio: ['ignore', 'pipe', 'inherit'] });
+
+// npm audit exits non-zero when it finds anything, so read its output regardless
+const audit = (cwd) => JSON.parse(spawnSync('npm', ['audit', '--json'], { cwd, encoding: 'utf8' }).stdout).vulnerabilities ?? {};
+
+// Packages with an advisory of their own, not the ones flagged only for depending on them
+const advised = (vulnerabilities) => Object.values(vulnerabilities).filter((v) => v.via.some((via) => typeof via === 'object'));
+
+const major = (version) => Number(version.split('.')[0]);
+
+const lockedMajors = (cwd, name) => {
+  const { packages } = JSON.parse(readFileSync(join(cwd, 'package-lock.json'), 'utf8'));
+  return Object.entries(packages)
+    .filter(([path]) => path.endsWith(`node_modules/${name}`))
+    .map(([, { version }]) => major(version));
+};
+
+const fixed = [];
+const crossMajor = [];
+const unfixed = [];
+
+for (const cwd of PACKAGES) {
+  // Lifecycle scripts stay off: this job holds a token that can write to the repo.
+  // Exits non-zero when it leaves anything unfixed, which the overrides below deal with.
+  spawnSync('npm', ['audit', 'fix', '--ignore-scripts'], { cwd, stdio: 'ignore' });
+
+  const path = join(cwd, 'package.json');
+  const manifest = JSON.parse(readFileSync(path, 'utf8'));
+  const direct = { ...manifest.dependencies, ...manifest.devDependencies };
+
+  for (const { name } of advised(audit(cwd))) {
+    // Dependabot updates direct dependencies, and npm refuses an override that disagrees with one
+    if (name in direct) continue;
+
+    const latest = npm(cwd, 'view', name, 'version').trim();
+    const crossesMajor = lockedMajors(cwd, name).some((m) => m < major(latest));
+    // A range, not an exact pin, so later patches aren't blocked the way 1.16.1 blocked 1.16.2
+    manifest.overrides = { ...manifest.overrides, [name]: `^${latest}` };
+    writeFileSync(path, `${JSON.stringify(manifest, null, 2)}\n`);
+    (crossesMajor ? crossMajor : fixed).push(`${cwd}: ${name} ^${latest}`);
+  }
+
+  npm(cwd, 'install', '--ignore-scripts');
+  unfixed.push(...advised(audit(cwd)).map(({ name }) => `${cwd}: ${name}`));
+}
+
+const report = [
+  ...fixed.map((line) => `- ${line}`),
+  ...crossMajor.map((line) => `- ${line} (new major version)`),
+  ...unfixed.map((line) => `- ${line} (still vulnerable, no fix found)`),
+].join('\n');
+console.log(report || 'No overrides needed.');
+
+if (process.env.GITHUB_OUTPUT) {
+  appendFileSync(process.env.GITHUB_OUTPUT, `cross-major=${crossMajor.length > 0}\nreport<<EOF\n${report}\nEOF\n`);
+}

.github/workflows/security-auto-fix.yml

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+name: Security auto-fix
+
+# Covers the alerts Dependabot security updates can't: it won't change `overrides` or move a
+# transitive package past its parent's range. Everything else still goes through Dependabot.
+on:
+  schedule:
+    - cron: '30 5 * * *'
+  workflow_dispatch:
+  push:
+    branches: [test/security-auto-fix]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: security-auto-fix
+
+env:
+  BRANCH: security/auto-fix
+
+jobs:
+  fix:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
+        with:
+          node-version-file: .nvmrc
+      - id: fix
+        run: node .github/scripts/fix-advisories.js
+      - id: changes
+        run: echo "found=$([ -n "$(git status --porcelain)" ] && echo true || echo false)" >> "$GITHUB_OUTPUT"
+      # A personal token, not GITHUB_TOKEN: GitHub holds CI on github-actions[bot] PRs for approval,
+      # so the checks the "Require CI" ruleset waits for would never run. Only this step gets it,
+      # so nothing npm installs can read it.
+      - if: steps.changes.outputs.found == 'true'
+        run: |
+          git config user.name 'github-actions[bot]'
+          git config user.email '41898282+github-actions[bot]@users.noreply.github.com'
+          git switch -C "$BRANCH"
+          git commit -am 'Fix npm security advisories'
+          git push --force "https://x-access-token:${GH_TOKEN}@github.com/${GITHUB_REPOSITORY}.git" "$BRANCH"
+          if [ -z "$(gh pr list --head "$BRANCH" --state open --json number --jq '.[].number')" ]; then
+            gh pr create --head "$BRANCH" --title 'Fix npm security advisories' --body "$REPORT"
+          fi
+          # Same policy as dependabot-auto-merge.yml: majors wait for a human
+          if [ "$CROSS_MAJOR" = 'false' ]; then
+            gh pr merge "$BRANCH" --auto --squash
+          fi
+        env:
+          GH_TOKEN: ${{ secrets.SECURITY_AUTOFIX_TOKEN }}
+          REPORT: ${{ steps.fix.outputs.report }}
+          CROSS_MAJOR: ${{ steps.fix.outputs.cross-major }}