HTML-Editor, save, change app, browser asks

I have an app for edit data in HTML-Editor.
If I change the data, click on the form save-button and then switch to another app, my firefox-browser asks: This page asks you to confirm that you want to leave the page - data you have entered will not be stored under certain circumstances. [stay] [leave]

what’s wrong here?

I am seeing the same thing with the Chrome browser. Surprised there has been no response on this.

Doesn’t seem to be related to any browser. I have tried them all and have the same in all browsers. Any update from anyone?