Woodpecker: Privilege escalation via unrestricted serviceAccountName in the Kubernetes backend

Woodpecker is a CI/CD engine. From 1.0.0 until 3.16.0, pipeline/backend/kubernetes/backend_options.go defines backend_options.kubernetes.serviceAccountName, and the Kubernetes backend in pipeline/backend/kubernetes/pod.go copies that pipeline-step value directly into the pod specification without administrator authorization. Any user with Push permission on a connected repository can therefore run pipeline pods under an arbitrary ServiceAccount in the pipeline namespace and inherit that account's RBAC permissions. When a privileged ServiceAccount is reachable, the attacker can exfiltrate secrets such as database credentials, API keys, and TLS certificates and may take over the cluster. This issue is fixed in version 3.16.0.