Sticky old nameservers

[Stephane Bortzmeyer]

On Wed, Feb 19, 2020 at 09:26:54AM +0100,
 Andreas Schwarz <andreas at black-code.de> wrote 
 a message of 105 lines which said:

> unbound-control lookup assemblee-nationale.fr

Unfortunately, this resolver does not have control enabled. (And, if I
restart it with 'control-enable: yes', the problem disappears, which
is good for operations but bad for science.)

> I occasionally have similar issues with my setup when a domain
> changes its nameservers. If I recall correctly, this is due to the
> domain's old nameserver to be asked being cached.

It is normal? I mean, it could enable "phantom domain" attacks.