avast free antivirus, firefox, and js:miner-ae [pup]

[REDACTED]

Hi. There's an avast message that says "Threat secured We've safely aborted connection on dementiafriendlyamericacitruscounty.org because it was infected with JS:Miner-AE [PUP].", which seems to appear every couple of minutes when browsing to different sites with firefox. Does anyone know if that's an issue with avast free antivirus, firefox, or something else, and is there a way to fix it? Let me know if you need any other information. Thanks.

avast free antivirus Program version: 18.8.2356 (build 18.8.4084.0), Virus definitions version: 181118-10
Firefox 63.0.3 64 bit
windows 7 home premium 64 bit

[Asyn]

Start a topic in V&W and post your logs there: https://forum.avast.com/index.php?action=post;board=4
Instructions (basic diagnostic logs): https://forum.avast.com/index.php?topic=194892.0