It seems like when someone reports a problem. (A guest) they can then post in that forum.

I have attached two screen shots

Your Font Awesome icons are not showing. I would start by going to the ACP support section and rebuilding your system cache. 

10 minutes ago, Stan Jensen said:

It seems like when someone reports a problem. (A guest) they can then post in that forum.

Where is the post in the forum?

if you are referring to the text starting with "I ve sponsored...." then that's the report the Guest submitted.

Advice: don't allow Guests to use the report system..edit the group, go to the 'Content' tab, find the indicated item.

Is that the same as clear cache?  I have done that.

What I want to know is how/why can a guest post?  or is that related?

Agree with Nathan, disable guests reporting content. 

Just now, Stan Jensen said:

What I want to know is how/why can a guest post?  or is that related?

You will want to see what Nathan posted:

1 minute ago, Nathan Explosion said:

Where is the post in the forum?

if you are referring to the text starting with "I ve sponsored...." then that's the report the Guest submitted.

Advice: don't allow Guests to use the report system..edit the group, go to the 'Content' tab, find the indicated item.

 

I have done so, but still, wondering why they were allowed to post, or is this a known issue?

1 minute ago, Stan Jensen said:

wondering why they were allowed to post

 

Are you referring to this content, or is there an actual post in the forum itself which you haven't included a screenshot of?

there are several responses in diverse places over the response to a post when it is reported by the guest. All the moderators get notified but have trouble finding it'

turning off the guest reporting should resolve that.

It does indeed look like its reports and not posts themselves. You can switch that off from your guests group