/usr/lib/ruby/vendor_ruby/ is in ruby-buff-extensions 1.0.0-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/
/usr/lib/ruby/vendor_ruby/buff-extensions.rb
/usr/lib/ruby/vendor_ruby/buff/
/usr/lib/ruby/vendor_ruby/buff/extensions.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/
/usr/lib/ruby/vendor_ruby/buff/extensions/kernel/
/usr/lib/ruby/vendor_ruby/buff/extensions/kernel/reporting.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/string.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/object/
/usr/lib/ruby/vendor_ruby/buff/extensions/object/try.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/object/blank.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/kernel.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/string/
/usr/lib/ruby/vendor_ruby/buff/extensions/string/inflections.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/object.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/boolean.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/version.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/dotted_paths.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/except.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/slice.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/key_transforms.rb
/usr/lib/ruby/vendor_ruby/buff/extensions/hash/reverse_merge.rb