When running the Firebase Emulator, you can update your Firebase Firestore and Storage security rules by changing the relative files firestore.rules and storage.rules.
Before deploying your application to your users, you need to make sure that you're also publishing the security rules from your Firebase Console.
Storage Security Rules
To publish your Firebase Storage security rules, navigate to the Firebase Console.
From the main sidebar, click on "Storage". Afterward, click on the "Rules" tab:
Afterward, paste the content from storage.rules to the text editor, and
click "Publish".
Firestore Security Rules
To update your Firestore Security rules, follow the same steps as for the Storage rules explained above.
Of course, the only difference is navigating to the Firestore tab, and
choosing the content of firestore.rules.