/usr/share/grub/default/grub.md5sum is in grub2-common 1.99-21ubuntu3.19.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | dfad90339e4227d432636ed7d4483744 experimental_1.96+20081129-1
e916b60d7de71969dd7bad5a809fb9dc lenny_1.96+20080724-16
965e5137eff659cded3adb640357c33d maverick_1.98+20100705-1ubuntu1
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