Hi,
I don't know if the previous answers helped you resolve your issue - I had the same issue and if it still persists, try the below. A little bit of a background, this issue occurs due to DNS poisoning. The short of it is that your router is now infected. If you're seeing adsmatte issue on your laptop/computer as well, this is most likely the case and I recommend resetting your router and changing the DNS server to a safer one (I'll describe this in just a second).
1) On your laptop/computer, open a command prompt (windows + r > 'command'). Type ipconfig. This will give you a list of active connections on your laptop, scroll till you find your Wifi or Ethernet connection details. Look for the words "Default Gateway", "Subnet mask", etc.
2) Once you've got your details, on your Lumia: Phone settings > Wifi > static IP > Flip "configure network settings manually" to "on"
3) Plug in the below values as follows:
- IP Address - input the 'IPv4 Address' from the ipconfig step. this will most likely be 192.168.1.x (x being some number between 1 - 255)
- Subnet mask - input the Subnet mask from the ipconfig step (should be 255.255.255.1 or 0)
- Default gateway - input the default gateway from the ipconfig step (will usually be 192.168.1.1)
- DNS - Use 8.8.8.8 or 8.8.4.4 (These are google DNS servers and are a safe bet - google them for more info).
Hit "Done" and wait for your phone to connect to the Wifi - load a few sites and you should no longer see the adsmatte issue.
It might not work on the first try - this could be due to the DNS server. I tried 8.8.8.8 at first, and not one website would load. Changing to 8.8.4.4 did the trick.
Hope this helps!
Phone Settings > Wifi > Static IP