Media attachments URL are a real problem in WordPress. Some developers of plugins have decided to redirect ALL media attachments to the homepage. They are wrong. One of my websites has been already penalized for such a behavior. Some developers of plugins decide to redirect media attachments to the parent page. They are wrong too. If you upload a picture to WordPress, and then if you go to the media library and click on view attachment page, you will be able to see the attachment page because it has no parent. It is normal since you didn't added the picture to a post or a page. When the picture isn't listed on a post or page, it still has an attachment page. So, some of you may say: "but I think that google will never find it". You are wrong! In fact, because of autocomplete function of wordpress and other auto guessing features of plugins, Google may follow a Url and end up on the attachment page. This plugin destroys media attachment by returning a 404. That's the best. Using this technique, it ensures that you will never get penalized because of the media attachment. The 404 is the best approach. I looked into the redirections when googlebot visited a Attachment URL using Yoast. GOoglebot expects a HTML page at the end of the redirection. However, Yoast redirects to an image. Let me explain. I saw that after hitting the attachment page and being redirected to the URK (for instance: /jojo.jpg). Google sends a HTTP request: "accept: text/html" in other words, google thinks that jojo.jpg is a HTML file. It is normal because the source is a HTML page (the attachment page). Googlebot does not like this redirection between it transits from a HTML page to a media file (for instance an image). Then, Googlebot is lost and will come back several time, looking for a text/html rather than a image/jpeg PLus, this plugin is super easy to use. You install it, activate it and it works out of the box.