A mystery field appears on all fluent forms on my WordPress web pages but this mystery field does not appear on the form

A mystery field appears on all fluent forms on my WordPress web pages but this mystery field does not appear on the form editor. How do I delete this mystery field? It's on all of my forms.

The mystery field also keeps changing names every time I refresh the page. Sometimes it says "Updates," "Subscribe," "Newsletter," or "Contact." 

If I recall correctly, the only new things I've done lately are to install the hCaptcha plug-in and the Yoast SEO plug-in.

Please help! Thank you!