Deleting a user in an external security realm did not invalidate their session or 'Remember me' cookie

When using an external security realm such as LDAP or Active Directory, deleting a user from the security realm does not result in the user losing access to Jenkins. While deleting the user record from Jenkins did invalidate the 'Remember me' cookie, there was no way to invalidate active sessions...

Ephemeral user record was created on some invalid authentication attempts

When attempting to authenticate using API token, an ephemeral user record was created to validate the token in case an external security realm was used, and the user record in Jenkins not previously saved, as legacy API tokens could exist without a persisted user record. This behavior could be...