Can someone please explain to me why an antivirus is telling me that my Wifi password is weak and then reveals it if I click on it? How on earth does it even know that my Wifi password is “weak”? I did not ask or approve that Avast should store any of my passwords, which is the reason I opted out of the password component they have!
1]
avast passwords has nothing to do with the scan/detection
2]
avast doesn’t store passwords
3]
avast is not just a anti-virus, it is much more.
True anti-virus software hasn’t been around for at least 15(!) years.
4]
There are many ways to check if a password is weak or not.
The length is just one of them.
5]
If avast says your password is weak it is time for you to change it to a strong password.
How on earth does it even know that my Wifi password is "weak"?When you loged in to your wifi network for the first time, you gave the network name and password to your OS And now your OS have given that info to avast .... wow
You may contact Bill Gates and complaine 
Do you really think that any app could not have access to this info? Just run in an admin command line:
netsh wlan show profile
then
netsh wlan show profile “NETWORK NAME” key=clear
Voilá…