The important info would be on the popup, so a screenshot would help
right click avast tray icon, select show last popup (does not work if you have rebooted)
in top right corner is a pin … click it and pin it to screen and take screenshot
WOT web rep report is clear about this fraudulent spam site: Canadian Pharmacy Spam Cybercrime Gang.
And listed in this blacklist: http://www.joewein.de/sw/blacklist.htm
Added it to third party lists in my uBlock Original adblocker option settings,
polonus (volunteer website security analyst and website error-hunter)