Multiple cybersecurity sources report that Chinese-made Zbtlink routers include a “factory-shipped” backdoor. Researchers say the implant enables remote access that can provide root-level control without authentication, including an “unauthenticated root shell.” The issue is described as present across a broad range of Zbtlink firmware versions available over an extended period. One report, attributed to VulnCheck, states the backdoor appears in all Zbtlink firmware images currently available, totaling 21 images, and spanning more than two years. The accounts also describe the backdoor as starting automatically when the device runs and then attempting to contact an external endpoint, described as beaconing to China. The reports indicate the affected scope includes at least 20 router models, based on the set of products and firmware variants reviewed by researchers. The disclosures focus on the backdoor’s behavior and technical characteristics rather than confirmed real-world exploitation. The information is presented as a vulnerability disclosure intended to inform users, network administrators, and manufacturers about potential unauthorized control risks.