JWTs  are a good storage candidate because they allow for the client to be responsible for keeping track of the permissions of the currently logged in user. This removes the need for a session store in most cases which dramatically increases scalability and there are no more potential problem of synchronizing the store among processes with separate memory.  However JWTs require a secret key to be decrypted which means it can't happen on the frontend with the same key that the server uses, say for its csrf protection. A malicious visiter would be able to download the source code compiled on a few different views and look for similar strings. One of them would be the secret key so its easily brute-forcible.