Debian 8.5 installation Media changes during install to 8.7


I've configured an "Operation System" for Debian 8.5.


After some month of installation I've also get automatically Debian 8.6 and


Without any work of myself. So it seems that even if I select my 8.5
Operation System at the end there is an actual Version (8.7 at this time)

So is it possible to fix it? If I select my 8.5 I will get 8.5? When I
start an installation with 8.5, at the End the Host have an operation
system 8.7

May be it 's possible to use the Installation Media URL with "$version,
$major and $minor" But I found nothing working for the Debian URL.


How did you all solve this?

best Regards,