```ts
/** The KEY=VALUE pairs of a config file. */
export function parseConfig(text: string): Record<string, string> {
  const config: Record<string, string> = {};
  for (const line of text.split("\n")) {
    if (line.trim() === "" || line.startsWith("#")) continue;
    const parts = line.split("=");
    if (parts.length !== 2) throw new Error(`Invalid configuration line: ${line}`);
    const key = parts[0].trim();
    if (key === "__proto__") throw new Error("__proto__ is not allowed in a config file");
    const value = parts.slice(1).join("=").trim();
    config[key] = value;
  }
  return config;
}
```