Facebook hits the Challenge page when sharing an article

Sometimes, when sharing an article on Facebook (either via a share button of by just putting the URL in a post box), Facebook hits the Cloudflare Challenge page. This causes the preview/post card to be the “Attention Required!” text, etc. (See below)

Now, I just can’t figure out why FB would ever hit that page. We have the normal WAF settings in place, as well as Rate Limiting on the (wordpress) login page.

Does anyone have an idea what could cause this to happen and above all: how I can prevent this?

You can try to whitelist Facebook’s network under https://dash.cloudflare.com/redirect?zone=firewall/tools

Thanks, I guess that’s the easiest solution.
I’ll try to find which IP-ranges they use. (Edit: sorry, I now get you actually gave me the proper ASN)

I’d still wonder why it would ever hit that Challenge page in the first place.