Is this hacking?

I have a “random posts” plugin, and I have just seen in one of those random posts that are being displayed, someone else’s website name as a post on my website!

I can’t find their website name in my comments section, or in my posts section.

My website is https://www.get-thin-for-good.com, but it may not be under “random posts” when you look, because obviously the posts change.

Would this be some kind of hacking? And if so, how can I protect my website? I don’t mind if I have to pay for protection!