JSON Web Token (JWT, suggested pronunciation /dʒɒt/, same as the word "jot"[1]) is a proposed Internet standard for creating data with optional signature and/or optional encryption whose payload holds JSON that asserts some number of claims.
If the other party, by some suitable and trustworthy means, is in possession of the corresponding public key, they too are able to verify the token's legitimacy.
This is because JavaScript running on the client-side (including browser extensions) can access these storage mechanisms, exposing the JWT and compromising security.
The content of the header might look like the following: This is a stateless authentication mechanism as the user state is never saved in server memory.
JWT implementations exist for many languages and frameworks, including but not limited to: JSON web tokens may contain session state.
While these vulnerabilities were patched, McLean suggested deprecating the alg field altogether to prevent similar implementation confusion.