Avast blocking multisite because of domain mapping

We have been having an issue in that Avast Free virus protection has been blocking all the sites in a multisite of ours.

See the forum post https://forum.avast.com/index.php?topic=177897.msg1260467#msg1260467

Now correct me if I am wrong but the code that appears to have caused this is from domain mapping.

If this is actually what happened I'm concerned that it might happen in other sites.

Can you give me some feedback. Has this occurred elsewhere. What can I do to stop it happening again?


  • Tyler Postle

    Hey Drew,

    Hope you're doing well today. That link is from the Domain Mapping single sign on feature. If you turn it off then it won't happen, I've attached a screenshot of the option to illustrate.

    This feature allows users to automatically sign into a mapped domain if they are already signed into the network. So when someone navigates from the original domain yourmultisite.com to mappeddomain.com they will still be signed in.

    This option is found via:

    Network admin > Settings > Domain Mapping.

    If you want to keep it on then you will want to make sure that it bypasses the url as it looks like the avast team member did in that thread you linked too.

    Let us know if you have further questions.

    All the best,

  • Tyler Postle

    Hey Drew,

    The reason that option exists is because you can't share cookies across domains, so by default when you login to the mainsite, you won't be logged into any of the mapped domains.

    That option automatically logs you in when you hit the mapped domain - so it gives the illusion of you being already logged into all the domains as you land on them.

    However, since Avast is looking for hidden iframes - according to that post you linked to - It must think that it's suspicious. Which it kind of is I suppose if you don't know what it's meant for - but we know that it's not something malicious. I don't have much experience with Avast, but assuming you are able to "whitelist" certain things, then it would be fine to whitelist this.

    Hope that helps!


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