```ruby
module Onebox
  module Engine
    class ImageOnebox
      include Engine

      matches_regexp /^(https?:)?\/\/.+\.(png|jpg|jpeg|gif|bmp|tif|tiff)(\?.*)?$/i

      def to_html
        # Fix Dropbox image links
        if /^https:\/\/www.dropbox.com/.match @url
          @url.gsub!("https://www.dropbox.com","https://dl.dropboxusercontent.com")
        end

        "<a href='#{@url}' target='_blank'><img src='#{@url}'></a>"
      end
    end
  end
end
```

Make dropbox image matching more strict
user
```ruby
module Onebox
  module Engine
    class ImageOnebox
      include Engine

      matches_regexp /^(https?:)?\/\/.+\.(png|jpg|jpeg|gif|bmp|tif|tiff)(\?.*)?$/i

      def to_html
        # Fix Dropbox image links
        if /^https:\/\/www.dropbox.com\/s\//.match @url
          @url.gsub!("https://www.dropbox.com","https://dl.dropboxusercontent.com")
        end

        "<a href='#{@url}' target='_blank'><img src='#{@url}'></a>"
      end
    end
  end
end
```
assistant