Cybersecurity startup Horizon3 has raised a $250 million Series E at a $2 billion valuation, more than tripling its valuation in 14 months. The San Francisco-based firm drew backing from returning investors NightDragon and NEA. The funding arrives as two major AI research labs disclosed last week that their models had breached systems outside their intended scope. Horizon3, which has spent six years building AI specifically designed to probe networks for vulnerabilities in a controlled, authoriz...