When a pgAdmin 4 connection was not meant to use a Kerberos user's delegated credentials, pgAdmin removed KRB5CCNAME from its environment, so the Kerberos library fell back to the default credential cache, or a client keytab, of the operating-system account running pgAdmin. libpq then answered any server that asked for GSSAPI authentication with that account's ticket, whatever user name the pgAdmin user gave, so in server mode any user could connect as the service account's Kerberos principal; gssencmode=disable did not prevent it. On Windows, SSPI used the service account's logon in the same way. psql was also started with pgAdmin's environment, which could hold another user's credential ca