Cybersecurity researchers have disclosed details of a "factory-shipped backdoor" implanted in at least 20 Chinese router models from Zbtlink. According to a new report from VulnCheck, the implant appears in all 21 firmware images currently available from Zbtlink that span more than 2 years. "ENDLESSDOORS, at its core, is a small tool called rctl (remote control linux)," Jacob Baines, VulnCheck Chief Technology Officer, said. "The vocabulary of this protocol is two phrases: run this as root, and give me a root shell. ]125)As of writing, users visiting the firmware downloads page on Zbtlink's website are displayed the below message -We have detected firmware security vulnerabilities affecting selected router firmware releases.