Horizon3, a cybersecurity company focused on security validation, announces a $250 million Series E funding round at a valuation of more than $2 billion. The round highlights continued investor demand for tools that can test and validate defenses more frequently than traditional, periodic pentesting, particularly as AI-enabled cyberattacks increase. TechCrunch and Help Net Security both report the same headline terms for the financing. Help Net Security adds that the company’s valuation rises sharply from about $650 million at its Series D, reached just over a year earlier, and says the Series E is oversubscribed. It also reports that existing investors NightDragon and NEA co-lead the round, with participation from seven new investors and five returning backers. Taken together, the coverage frames the funding as support for ongoing, automated security testing approaches designed to keep pace with rapidly evolving threats, including those that leverage AI. The reports do not describe changes to Horizon3’s product scope or customers beyond emphasizing the market need for continuous security validation.