Many Netgear routers have a remote authentication bypass bug.

This means malware or miscreants that are on your network, or anyone else is able to reach the device's web-based configuration interface, can gain control without having to provide a password.

Just stick the following in the URL to gain full access:

&genie=1

https://kb.netgear.com/000045848/Security-Advisory-for-Password-Recovery-and-File-Access-on-Some-Routers-and-Modem-Routers-PSV-2017-0677