This release contains the public artifact for the paper "When the Aggregator Cheats: Data-Free Backdoors in Federated LLM-based QA Systems" accepted to USENIX Security 2026. The artifact includes source code, scripts, configurations, documentation, and example commands for inspecting and reusing the implementation, and a supplementary document containing the complete per-dimension metric tables omitted from the paper due to space constraints. Attack-ready poisoned corpora, deployment payloads, complete trigger-target lists, private logs, API keys, cached checkpoints, and licensed third-party datasets/model weights are not included.