The TELNET service on the ZTE ZXV10 W300 router 2.1.0 has a hardcoded password ending with airocon for the admin account, which allows remote attackers to obtain administrative access by leveraging knowledge of the MAC address characters present at the beginning of the password.
https://exchange.xforce.ibmcloud.com/vulnerabilities/90958
http://www.securityfocus.com/bid/65310
http://www.kb.cert.org/vuls/id/228886
http://packetstormsecurity.com/files/125142/ZTE-ZXV10-W300-Hardcoded-Credentials.html
http://blog.alguien.at/2014/02/hackeando-el-router-zte-zxv10-w300-v21.html