Horizon3 Raises $250 Million Series E at Over $2 Billion Valuation to Expand Autonomous AI Penetration Testing

Funding Horizon3 Raises $250 Million Series E at Over $2 Billion Valuation to Expand Autonomous AI Penetration Testing Published August 3, 2026 By Antoine Tardif, CEO & Founder of Unite.AI Add Unite.AI to your preferred sources on Google Horizon3 has raised $250 million in Series E funding at a valuation exceeding $2 billion, giving the cybersecurity company substantial new capital to expand its autonomous penetration-testing platform and move further into automated defensive remediation.The round was co-led by existing investors NightDragon and New Enterprise Associates (NEA). Horizon3 says its valuation has more than tripled from the $650 million valuation attached to its Series D just over a year ago.The financing arrives as security teams face an increasingly difficult imbalance. Artificial intelligence can help attackers identify weaknesses, adapt techniques and move through compromised environments more quickly, while many organizations still depend on vulnerability scans and periodic penetration tests that provide only a snapshot of their security posture.Horizon3 is betting that organizations will respond by continuously attacking their own infrastructure before someone else does.Turning Penetration Testing Into a Continuous ProcessHorizon3 is the company behind NodeZero, a platform designed to autonomously conduct penetration tests against internal networks, external infrastructure, cloud environments, Kubernetes deployments and other components of an organization’s technology stack.Rather than simply generating a list of known vulnerabilities, NodeZero attempts to exploit weaknesses and combine them into complete attack paths. A misconfiguration might expose credentials, for example, which could then provide access to another system and eventually lead to sensitive data or administrative privileges.This approach is intended to distinguish between vulnerabilities that theoretically exist and weaknesses that can actually be used to cause meaningful damage.During a test, organizations can observe the techniques being executed through a real-time interface. Once testing is complete, the platform provides proof of exploitation, maps the steps taken through the environment and recommends actions for disrupting the attack path. Security teams can then rerun the relevant test to verify that a repair was effective.NodeZero can also identify problems that do not depend on a conventional software vulnerability, including weak passwords, exposed credentials, ineffective security controls, data leakage and poor network segmentation. Its internal tests can pivot from on-premises systems into services such as Amazon Web Services, Microsoft Azure and Microsoft 365 when an exploitable path exists.The broader objective is to replace occasional assessments with a repeating cycle of finding weaknesses, fixing them and testing the same environment again.How Horizon3 Uses AI Without Giving It Complete ControlAlthough Horizon3 describes NodeZero as an autonomous AI hacker, its architecture is more controlled than that phrase may suggest.The platform combines graph-based reasoning, machine learning, deterministic logic and narrowly scoped generative AI. It builds a map of systems, users, credentials and relationships within an envir