False Positive, its been reported several times.
And GOG is only doing what its doing, report it to avast, sometimes virus scanner engines are overzealous.
blaming gog is the wrong way to go.

I think blaming the people programming their updater to behave like a virus is perfectly reasonable. Updates for other software I have doesn't trip it. Also, how can I update if the file gets quarantined instantly?

To avast anything behaves like a virus, seriously their engine is overzealous so I blame them, thats why I stopped using avast.

You will have to wait until Avast updates since you refuse to turn off avast while Galaxy Updates/Installs, or add Galaxy to the exceptions.

Avast is blocking it on "reputation". AKA, "We haven't seen this file. It's new." The silly part is you can't tell it just to ignore that file.

cant play spellforce 3 becuase of this, and no way to ignore it

Right click your avast taskbar icon. Click 'Virus Chest', Avasts Virus Chest will
open showing all quarantined apps. Right click the one you want to return and
add exception to. Problem resolved. Happens to me on a few of my apps. Hope
this helps.

Avast detected personal word documents as malicious and locked me out of them unless I uploaded them to Avast's team to investigate. That was before they added an exclusions feature, but I don't advise using terrorist software like theirs.

Terrorist software is a bit much, "not properly programmed" or "overzealous" would be more accurate.

Same is happening to me with AVG, it reported GalaxyUpdater.exe as filerepmalware and win32:Malware-gen.

I am having trouble with Avast all of suddenly blocking my updater.

Nope, still doesn't work. I've added both paths to exeptions in avast and still nothing, fail during instalation. I had to uninstall gog because it somehow, deleted the files.

OK, there is a walk around which works (adding paths to excluded doesn't). In avast you have to reset it to its basic settings, and then restart the PC. This way you wouldn't have to stop avast from protection and Galaxy would install without problems. Cheers.

This did nothing. On the next update attempt the file was quarantined again. I changed from Avast to Kaspersky Free. Perhaps it will do me until my license with Avast runs out and I can buy another good AV that actually catches things. Kaspersky has good ratings, but I'm leery to trust it. But since Avast is blocking some programs and people want to shit on it for doing its job rather than GOG for not making their updater like others do where virus scanners won't pop it, I need a protection that may be less secure so that GOG can go along GOGging.

Thanks for the update. It's nice to see you guys do care! :) Thank you so much on behalf of everyone suffering from this for at lest attempting to fix this issue. I for one am greatly appreciative.