Unhandled Rejection (SecurityError): The operation is insecure. On a fresh create-react-app project

Question

I created a new project with create-react-app then ran npm start then this showed up. https://imgur.com/a/3By9NCr

Using FF 69.0.3

Answer 1

Another solution found in the link in the answer by Niraj Niroula:

If you want to keep the Delete cookies and site data when Firefox is closed option enabled, click on the Manage Exceptions button and add localhost (with the protocol and port) to the exceptions list: