/usr/share/postgresql/9.3/extension/cube.control is in postgresql-contrib-9.3 9.3.24-0ubuntu0.14.04.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | # cube extension
comment = 'data type for multidimensional cubes'
default_version = '1.0'
module_pathname = '$libdir/cube'
relocatable = true
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