I have the same issue. Reboot, new session of FireFox, and the popup from Avast every 30 seconds telling me the same thing;
"Threat secured We've moved coinhive.min[1].js to your Virus Chest because it was infected with JS:Miner-C[Trj]."
I have ran a scan with no findings, rebooted, and did the same again with no results, yet this stupid things keeps popping up and ruining my day. Because I can't find an explanation or resolution, the only option I see is to switch virus software and remove Avast, since that is where the pop up is coming from, and there doesn't appear to be a resolution here. Before I do that, is there any other suggestion I should try before jumping off the cliff? BTW - While I might be considered an advanced user, I am not the guy that's going to look at codes and things, I just need it to work. If there is anything beyond a regular resolution, let me know that too.
I thank anyone for their feedback and opinion in advance.
OffDWall