/usr/lib/ruby/vendor_ruby/ is in ruby-chunky-png 1.2.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/chunky_png/
/usr/lib/ruby/vendor_ruby/chunky_png/canvas.rb
/usr/lib/ruby/vendor_ruby/chunky_png/color.rb
/usr/lib/ruby/vendor_ruby/chunky_png/datastream.rb
/usr/lib/ruby/vendor_ruby/chunky_png/rmagick.rb
/usr/lib/ruby/vendor_ruby/chunky_png/palette.rb
/usr/lib/ruby/vendor_ruby/chunky_png/image.rb
/usr/lib/ruby/vendor_ruby/chunky_png/point.rb
/usr/lib/ruby/vendor_ruby/chunky_png/vector.rb
/usr/lib/ruby/vendor_ruby/chunky_png/chunk.rb
/usr/lib/ruby/vendor_ruby/chunky_png/compatibility.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/png_decoding.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/data_url_exporting.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/drawing.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/stream_importing.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/resampling.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/masking.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/data_url_importing.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/stream_exporting.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/png_encoding.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/adam7_interlacing.rb
/usr/lib/ruby/vendor_ruby/chunky_png/canvas/operations.rb
/usr/lib/ruby/vendor_ruby/chunky_png/dimension.rb
/usr/lib/ruby/vendor_ruby/chunky_png.rb