AVG anti-virus warning seeming to come from Firefox Metamask plugin, despite this being a fresh windows install

I do not understand enough about this to diagnose, and it seems strange to me that this is possible on a fresh Win10 installation (even the RAID5 got pulled apart, reformed, and renamed), but for some reason, AVG reports this fishing thing when I open the Firefox browser:

"metamask.github.io/phishing-warning/v3.0.3/favicon.ico"

Rebooting doesn't help, the moment Firefox is opened, AVG reacts.

So this laptop doesn't have much reinstalled on it since the hard drive was formatted, just a memtechtips (see youtube channel) and christitustool modified install, so it is barebones win10pro, with firefox thunderbird steam zoom signal skype vlc notepad++ and a few other things, nothing that should be in any way compromised ...

... only disabling the firefox plugin stops it:

I don't know what else to tell you, because I am stumped, but if there is anything you want me to test and report back, let me know.

The report concerns the Firefox MetaMask plugin and the URL metamask.github.io/phishing-warning/v3.0.3/favicon.ico; no source file or test is identified. Start by reproducing the AVG alert when Firefox opens with the plugin enabled, then determine whether the warning is expected and record a confirmed cause and resolution.

Written by the indexing model from the issue text.