Why is my website adding a span with id PING_IFRAME_FORM_DETECTION to the bottom of the page?

I have a React/Node website created using Vite. On pages that have a form, when any of the inputs are put into focus for the first time, the following element is added to the bottom of the page. I can’t find this id anywhere in any dependency, in my project, and can’t find any information about it when searching the internet. I’m completely lost here.

<span id="PING_IFRAME_FORM_DETECTION" style="display: none;"></span>