I've noticed that when I attach an image to a post, two URLs are generated, not just one:http://www.example.com/?attachment_id=1782http://www.example.com/blog/2014/09/26/some-article/attachment/the-title-of-the-image/This leads to duplicate titles in Google Webmaster Tool. I'm in the process of creating 301 redirects to avoid this but it is painful.Is it normal behaviour of Wordpress ? 
Google Webmaster Tool : duplicate title with wordpress media
google search console;wordpress;duplicate content
I would use Yoast's SEO plugin to fix this. There is a setting which will redirect image attachments to the parent post. All done for you so no need to do anything manually. Go under Advanced, click Permalinks tab and check the second option:or you can just setup something in .htaccess file to do the same.