When you login to Identityserver the authentication cookie idsrv is stored in the browser. When the user logs out, the cookie is deleted. However, an attacker can steal the cookie and essentially use it even though the user has logged out.
This seems to be "normal" behavior for many identity providers too.
Question
Is it accepted behavior?
Is there anyway to detect that the user has logged out and that the idsrv cookie value (token) is no longer valid? Should we for example implement IAuthenticationSessionValidator to keep track of the users that are signed out? Or is this something that should belong to the application by using the id_token session_state claim?