Comment by jacopofar2

The "none" algorithm set in header is a well known problem and, for example, nodejs most used library automatically uses asymmetric keys when one is given, ignoring the header (https://github.com/auth0/node-jsonwebtoken/blob/master/verif...)

As long as the problem is known to the developers and the key is specified, I think the biggest issue of JWT is the lack of session invalidation (that is, if you log out your already emitted tokens are still valid until their expiration), but it's a good tradeoff for not having server sessions.