The Debian Stretch installation page ( https://www.debian.org/releases/stretch/debian-installer/ ) has been updated to point at 9.8.0 with the release of Buster, but the latest release is 9.9.0. See also: https://salsa.debian.org/webmaster-team/webwml/commit/ce055afb982d70f75fd64508543ef5517373b982
Unrelated to the main topic, the "installation report"-link in the errata section of the same page appears to be broken (seems to affect all release pages). Regards, Niklas