WebApp Offensive Security Engineer

Get to Know Us Horizon3.ai is a fast-growing, remote cybersecurity company dedicated to the mission of enabling organizations to proactively find and fix and verify exploitable attack vectors before criminals exploit them. Our flagship product, the NodeZeroTM platform, delivers production-safe autonomous pentests and other key assessment operations that scale across the largest internal, external, cloud, and hybrid cloud environments. NodeZero has been adopted by organizations of all sizes, from small educational institutions to government agencies and Global 100 enterprises. It is used by ITOps/SecOps teams, consulting pentesters, and MSSPs and MSPs. We are a fusion of former U.S. Special Operations cyber operators, startup engineers, and formerly frustrated cybersecurity practitioners. We're committed to helping solve our common security problems: ineffective security tools, false positives resulting in alert fatigue, blind spots, "checkbox” security culture, cybersecurity skills shortage, and the long lead time and expense of hiring outside consultants. Collectively, we are a team of learn it alls, committed to a culture of respect, collaboration, ownership, and results. Summary We're looking for a Webapp Offensive Security Engineer with deep, hands-on web application penetration testing experience to push our autonomous testing beyond what it can do today. You'll be testing real customer web applications — not just labs and benchmarks — using NodeZero as your starting point and then going further as the human expert: hunting the edge cases, novel attack chains, and business-logic flaws that automated testing doesn't yet handle, proving them out safely against live targets, and working shoulder-to-shoulder with our software engineers to turn each discovery into durable product coverage that benefits every customer. This is a pentesting-first role. You won't be expected to architect platform internals or ship production features yourself — you'll be the offensive expert who tests live customer applications, finds the gaps NodeZero doesn't yet cover, demonstrates them, defines what "good" looks like, and partners with engineering to close them. If you love breaking real web apps by hand, get satisfaction from finding what scanners miss, and want your tradecraft to scale to thousands of customers through the product, this role is for you. Essential Functions - Perform hands-on, full-scope web application penetration tests against real customer applications, alongside benchmark and lab targets, to surface vulnerabilities and attack paths. - Review NodeZero results on live customer engagements to identify coverage gaps, blind spots, and missed opportunities — the edge cases and corner-case attack scenarios that autonomous testing doesn't yet handle. - Manually reproduce and validate those edge cases, building reliable, production-safe proof-of-concept exploits and clear test cases that demonstrate the gap end to end — including against live customer environments without disrupting them. - Partner closely with software engineers to translate your findings into product improvements — defining detection logic, attack content, expected behavior, and remediation so NodeZero handles those cases going forward. - Build and maintain a library of regression and benchmark test cases so newly added coverage doesn't silently regress over time. - Monitor production pentests for missed findings and false positives; create and triage Jira tickets to drive issues to resolution. - Work directly with customers and internal teams to investigate findings, explain attack paths, and address questions about web application coverage and results. - Author technical blog posts and research write-ups showcasing new exploits, edge cases, and attack methodologies. - Mentor teammates and contribute to continuous improvement of team processes, methodology, and testing standards. Competencies/Requirements - Extensive hands-on experience conducting full-scope we