/usr/lib/cruft/explain/doc-base is in cruft-common 0.9.34.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 | #!/bin/dash
# files generated by doc-base, eg. /usr/share/doc/xterm-faq/.dhelp, if any
set -e
if [ ! -d /var/lib/doc-base/info ]; then exit 1; fi
find /var/lib/doc-base/info -mindepth 1 -maxdepth 1 -name '*.list' -print0 | xargs -r0 cat
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