The ZTE ZXV10 W300 router contains hard-coded credentials that are useable for the telnet service on the device. The username is "admin" and the password is "XXXXairocon" where "XXXX" is the last four characters of the device's MAC address. The MAC address is obtainable over SNMP with community string public.
f4ed8e390aaf0ec726b015355351d5726098fe77192fb55fc5a05886a6f225ce