For the past few weeks on all my PC’s I keep getting this message popup window, and have no clue why, and how to resolve this matter, nothing has changed on my router setup.
See pic below of pop up window, am I the only one that has reported this or is getting this message, I did a search and nothing came up.
Please attach your screenshot(s), some of us don’t follow external links. 
Realtek PCIe GBE family controller
Is not properly secured, this network could expose your private data
https://forum.avast.com/index.php?action=dlattach;topic=235261.0;attach=213981;image
There you go, Picture should be posted above now
Interesting, nothing I’ve ever seen before. Wait for one of the devs…
Still no response from anyone from the Avast Team ??
Wow, amazing no replies here, this message I get every now and then on a few devices and not all on the same network. Still curious what this means 8)
I just installed a StarTech [Realtek] PCI (not"e") gigabit adapter on a Win 10 desktop so I thought I should just check w/Avast WiFi Inspector to see if I got the same error. That scan turned up no error and I haven’t seen any popups like you have shared. Perhaps its the difference between PCI and PCIe versions of the adapter. I should mention that I did update the default Microsoft driver (circa 2015 IIRC) with a more recent one (2017 v 10.23.1003.2017) from Realtek website. Might be worth checking while you’re waiting for response from devs… 
Edit: missed a “)”