Threats blocked repeatedly, source unclear.

[Jules12]

Hey, I keep getting the notifications that

1. We've blocked a threat URL:Blacklist on [URL1] from being downloaded.
2. We've blocked a threat URL:Malvertising on [URL2] from being downloaded.

The URL for format 1 is always the same. The URL for format 2 is always the same. This happens over and over. I'm not actively attempting to access these urls at all, so I'm concerned I have a malware infection that's trying to access them. Avast hasn't located anything, though. Is there something I can or should do, or is this just something I have to put up with?

[DavidR]

I'm totally unfamiliar with Apple Macs.

But in Windows this is generally a problem with your browser, you could try using a different browser for a time and see it also happens with that.

For the Windows side this is the general advice we would give.
As you weren't intending to visit the site:
Start by clearing your browser cache and cookies, including 3rd party cookies and restart your browser.
If that resolves it you should be good to go.
If it doesn't try running your browser with add-ons disabled.

If that resolves it, have you added or updated any add-ons ?