/usr/lib/ruby/vendor_ruby/ is in ruby-escape-utils 1.1.0-1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/escape_utils/
/usr/lib/ruby/vendor_ruby/escape_utils/html_safety.rb
/usr/lib/ruby/vendor_ruby/escape_utils/javascript/
/usr/lib/ruby/vendor_ruby/escape_utils/javascript/action_view.rb
/usr/lib/ruby/vendor_ruby/escape_utils/url/
/usr/lib/ruby/vendor_ruby/escape_utils/url/erb.rb
/usr/lib/ruby/vendor_ruby/escape_utils/url/uri.rb
/usr/lib/ruby/vendor_ruby/escape_utils/url/cgi.rb
/usr/lib/ruby/vendor_ruby/escape_utils/url/rack.rb
/usr/lib/ruby/vendor_ruby/escape_utils/html/
/usr/lib/ruby/vendor_ruby/escape_utils/html/erb.rb
/usr/lib/ruby/vendor_ruby/escape_utils/html/haml.rb
/usr/lib/ruby/vendor_ruby/escape_utils/html/cgi.rb
/usr/lib/ruby/vendor_ruby/escape_utils/html/rack.rb
/usr/lib/ruby/vendor_ruby/escape_utils/xml/
/usr/lib/ruby/vendor_ruby/escape_utils/xml/builder.rb
/usr/lib/ruby/vendor_ruby/escape_utils/version.rb
/usr/lib/ruby/vendor_ruby/escape_utils.rb