/usr/lib/ruby/vendor_ruby/ is in ruby-loofah 2.0.3-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/loofah/
/usr/lib/ruby/vendor_ruby/loofah.rb
/usr/lib/ruby/vendor_ruby/loofah/elements.rb
/usr/lib/ruby/vendor_ruby/loofah/helpers.rb
/usr/lib/ruby/vendor_ruby/loofah/html/
/usr/lib/ruby/vendor_ruby/loofah/html/document.rb
/usr/lib/ruby/vendor_ruby/loofah/html/document_fragment.rb
/usr/lib/ruby/vendor_ruby/loofah/html5/
/usr/lib/ruby/vendor_ruby/loofah/html5/scrub.rb
/usr/lib/ruby/vendor_ruby/loofah/html5/whitelist.rb
/usr/lib/ruby/vendor_ruby/loofah/instance_methods.rb
/usr/lib/ruby/vendor_ruby/loofah/metahelpers.rb
/usr/lib/ruby/vendor_ruby/loofah/scrubber.rb
/usr/lib/ruby/vendor_ruby/loofah/scrubbers.rb
/usr/lib/ruby/vendor_ruby/loofah/xml/
/usr/lib/ruby/vendor_ruby/loofah/xml/document.rb
/usr/lib/ruby/vendor_ruby/loofah/xml/document_fragment.rb