Browser security startup Island raises $400M at $6.4B valuation to defend against rogue AI agents

Browser security startup Island has raised $400 million at a $6.4 billion valuation as companies confront a new security problem: AI agents that can browse websites, access corporate systems, handle files, and take actions with far less human supervision.

The Dallas-based startup announced the funding Thursday, with Evolution Equity Partners leading the round. Island plans to use the new capital for research and development and international growth across Europe, Asia, and the Middle East. The company expects to grow from roughly 1,000 employees to 1,500 by mid-next year.

The latest funding comes just six months after Island’s Series E round. TechStartups featured the company in March when the cybersecurity startup raised $250 million at a $4.8 billion valuation amid growing demand for secure enterprise browsers. The new round lifts Island’s valuation by $1.6 billion in just half a year.

The timing is hard to miss. Companies spent years securing what employees could do inside a browser. AI agents are changing that equation by introducing software that can perform many of those same actions on a user’s behalf.

“Every old control is breaking, so everything’s up for grabs,” Island CEO and co-founder Mike Fey told CNBC. “I’ve never seen anything like it. It’s a very special time.”

That concern has moved beyond hypothetical security exercises. Rogue AI agents have drawn greater scrutiny following incidents involving autonomous systems taking unexpected or unauthorized actions, including OpenAI’s previously reported agent-orchestrated attack on Hugging Face. Just last week, OpenAI disclosed six new cases of “concerning” AI model behavior beyond the Hugging Face incident.

For businesses, the issue goes beyond blocking malicious AI. Companies are starting to deploy their own AI agents across workflows that touch email, documents, internal applications, customer data, and the open web. Each new capability creates another question for security teams: What should an agent be allowed to see, and what should it be allowed to do?

The browser is becoming an AI security checkpoint

Island is betting that the browser can become one of the places where companies answer those questions.

Founded as an enterprise browser company, Island gives businesses greater control over browser activity without forcing employees into a collection of separate security products. Its customers include Pfizer, Chipotle, American Airlines, and major financial institutions. The company ranked No. 28 on CNBC’s 2026 Disruptor 50 list.

Browsers were already attractive targets for attackers. They sit between employees and many of the applications businesses depend on every day, making them a natural place to steal credentials, capture sensitive information, or gain access to corporate systems.

AI agents raise the stakes. A compromised employee account can give an attacker access to one user’s browser session. An improperly controlled agent could potentially operate across applications at machine speed, making permissions, identity controls, and visibility into browser activity far more important.

“What we’re focused on is enabling everything required for safe, secure, and productive capabilities for the future workforce,” Fey said.

Island isn’t alone in chasing the opportunity. Established cybersecurity companies such as Palo Alto Networks and a growing field of startups are developing products to secure AI systems, agents, identities, and the data they can reach.

That competition is creating another problem for corporate buyers: more security products can mean more software to integrate, monitor, and pay for. Island is betting that consolidating more of those controls inside the browser can give it an advantage.

Fey’s pitch is less complicated.

“It’s really simple: Have a much better product,” he said. “That’s your only option, and that’s what we’ve done.”

A $6.4 billion valuation suggests investors are betting that enterprise browsers will become more valuable as AI agents spread through corporate networks. The larger question is whether the browser becomes one of the main control points for the AI workforce now beginning to work alongside humans.

Island Co-founders