Command injection vulnerability in Linksys MR8300 router while Registration to DDNS Service. By specifying username and password, an attacker connected to the router's web interface can execute arbitrary OS commands. The username and password fields are not sanitized correctly and are used as URL construction arguments, allowing URL redirection to an arbitrary server, downloading an arbitrary script file, and eventually executing the file in the device. This issue affects: Linksys MR8300 Router 1.0.