TYPO3 Core

When you alter data in a CE and leave the CE via "Close" button, it shows a modal with "You have unsaved changes, would you like to save and close, continue editing, or discard them".

However, this is not always shown.

So far I have not identify when it shows and when not, however It works on some flexform fields and on some it doesnt.
For instance the ext:news (version 7.2.0) adds a flexform field "Max width for media elements" for FE Plugin "List of selected items". If you enter data in there and decide to close the CE, it shows the modal.

If you enter data via the wizard for the field "PageId for single news display" however, the modal is not shown and you simply silently discard the changes to the plugin - leaving the CE without saving.

So my best guess its some kind of flexform wizard thing maybe.

Tested versions:
Standard ext:news 7.2.0
TYPO3 9.5.8
nginx-fpm with php 7.2.19