@asymmetric-effort/nogginlessdom's Path Traversal in matchFileSnapshot allows arbitrary file write

export function matchFileSnapshot(actual: unknown, filePath: string): void {
  const serialized = serialize(actual);
  const mode = resolveUpdateMode();
  const fileExists = fs.existsSync(filePath);

  if (!fileExists) {
    if (mode === 'all' || mode === 'new') {
      const dir = path.dirname(filePath);
      if (!fs.existsSync(dir)) {
        fs.mkdirSync(dir, { recursive: true });
      }
      fs.writeFileSync(filePath, serialized, 'utf-8');

import { expect, setUpdateMode } from '@asymmetric-effort/nogginlessdom';

setUpdateMode('all');

// Writes arbitrary content to any writable path
expect('malicious content').toMatchFileSnapshot('/tmp/exploit/payload.txt');

// Path traversal via relative components
expect('data').toMatchFileSnapshot('../../../tmp/evil.txt');

// In CI environments, could overwrite CI config
expect('injected step').toMatchFileSnapshot('/home/runner/.github/workflows/backdoor.yml');

export function matchFileSnapshot(
  actual: unknown,
  filePath: string,
  projectRoot?: string,
): void {
  const root = projectRoot ?? process.cwd();
  const resolved = path.resolve(root, filePath);
  if (!resolved.startsWith(root + path.sep) && resolved !== root) {
    throw new Error(
      `File snapshot path must be within the project directory: ${filePath}`,
    );
  }
  // ... all subsequent file I/O uses `resolved` instead of `filePath`
}