Browser-based attacks are not new in the malicious landscape of attack patterns. Browsers remain a popular infiltration method for attackers. While seemingly local, services running on localhost are accessible to the browser using a flaw we found, exposing the ports on the localhost network interface, and leaving the floodgates ajar to remote network attacks. In this live demo and attack simulation we’ll unveil a zero-day vulnerability (still under responsible disclosure) in Chrome and other browsers, and how we use the 0-day to attack developers behind firewalls. We will demonstrate remote code execution on a wildly popular open-source platform serving millions in the data engineering ecosystem, that seems to run on localhost. In our talk, we will present novel attack techniques, targeting developers and employees within an organization, that are behind firewalls. This will be a first-ever deep dive into this newly discovered zero-day vulnerability.