This issue is fired when the preview of your test version is not protected by any username/password combination. It is considered an issue because your test version may contain some test pages or test data that you don't want to be publicly accessible.

This issue only appears if you have a Paid Plan on your Bubble application, as you cannot protect your test version on the Free Plan.

To protect your test version with a username/password combination, go to "Settings > General" on your Bubble application, and check this box:

And define a username and a password for your test version.

Please do not use the default "username/password" combination, which is really low-security. Change it to something personal, that couldn't be guessed by anyone else than you.