Senior Security Engineer

Mattermost is the leading collaborative workflow platform for defense, intelligence, security, and critical infrastructure. Trusted by the U.S. Department of War and Fortune 500s, our platform runs on-premises and in private clouds, delivering secure messaging, file sharing, workflow automation, audio/screenshare, and project management—all with full data and operational control. Mattermost powers high-stakes workflows across mission planning, real-time, real-world operations, DevSecOps, incident response, and cyber defense—enabling secure collaboration from tactical edge and DDIL environments to enterprise HQ. Teams operate across web, desktop, and mobile, with embedded interoperability for Microsoft Teams, Outlook, and Microsoft 365. To learn more, visit www.mattermost.com We are hiring a Senior Security Engineer to protect the people, infrastructure, and tooling that goes into building and hosting Mattermost. This is a hands-on, high-impact role at the intersection of enterprise security engineering, cloud information security, and AI-enabled threat response. Why Join Mattermost Fully remote, globally distributed team | no commute, genuine flexibility Be a key voice in shaping and delivering security strategy Competitive salary, equity, and benefits with meaningful work attached The Role As a Senior Security Engineer, you will lead the design and implementation of security t