/usr/share/thumbnailers/exe-dll-msi.thumbnailer is in gnome-exe-thumbnailer 0.9-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | [Thumbnailer Entry]
TryExec=/usr/bin/gnome-exe-thumbnailer
Exec=/usr/bin/gnome-exe-thumbnailer %i %o %u
MimeType=application/x-ms-dos-executable;application/x-msdownload;application/x-msi
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