Blocking of site: HTML:iframe-inf[Susp]

I’m getting blocked with this when I want to go to https://hkv-genealogie.nl/humo-gen/admin/index.php?page=editor&menu_tab=person&tree_id=10&person=I62758
Avast gives this: e3b103a6221c/2023-04-22T16:46:31.565Z (see attachment)
What exactly is the problem (how can I check it is not a false positive) and what can I do about this?

Do not know it is browser related, on chromium site is not being blocked.
Did you inform Antagonist BV?

See: https://en.internet.nl/site/hkv-genealogie.nl/2052515/

pol

Site is only blocked for online updating (need to be a user with update rights to access that page).

As Polonus already mentioned, contact the website.

I rebooted the computer I used to access the site in the mean time and I’m not getting the message anymore.
I would like to know more about the message before I do that.

Only Avast can supply that information.
Polonus and I are users not Avast employees.
Try contacting them:
Request help from Avast - https://support.avast.com/en-ww/contact/

Thanks, I’ll do that