https://micronews.debian.org/2023/1702150551.html
Due to an issue in ext4 with data corruption in kernel 6.1.64-1, we are pausing the 12.3 image release for today while we attend to fixes. Please do not update any systems at this time, we urge caution for users with UnattendedUpgrades configured. Please see bug# 1057843: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1057843
I just tried to update and it failed with error 403 when it tried to download the kernel, so it seems like they took measures.