I had this happen on my router. It hijacked the DNS for google-analytics.com and fed in some javascript that, on click, opened ad popups. I was able to solve it

I had this happen on my router. It hijacked the DNS for google-analytics.com and fed in some javascript that, on click, opened ad popups. I was able to solve it by hardcoding the DNS servers to 8.8.8.8 and haven't had any other problems.