A least privilege self-hosted instance is the best defense against that moment. It means every account, process, and subsystem has only the permissions it needs—nothing more. By cutting attack surfaces down to their smallest size, you make lateral movement nearly impossible for attackers and drastically limit the blast radius of human errors.
Start by defining roles with absolute precision. Map out the permissions each role needs to perform core functions. Deny all by default. Grant access explicitly, not implicitly. Use audit logs to monitor every access change, and ensure those logs are immutable. If you run containerized workloads, enforce least privilege at the container level too, not just at the host or application layer.
For a self-hosted instance, isolation is your ally. Keep services in separate namespaces, confine them with strict network rules, and avoid running anything as root unless there is no alternative. Use filesystem permissions to harden data directories, and pair them with application-level authorization to ensure no single control point can fail open.