Magda Sicknick

<ul>
<li>Redirects attachment pages to the parent post, or home page if no parent post exists. </li>
<li>Hides permalinks when editing/uploading attachments. </li>
<li>Disables ‘Link to’ option when inserting media to a post/page.</li>
</ul>

WP Disable Attachment Pages

Redirects attachment pages to the parent post, or home page if no parent post exists.

tamlyn

Unattach is a very simple plugin which allows detaching images and other media from WordPress posts, pages and other content types.
As of WordPress 4.2 this functionality is built in. For previous versions, the only way to detach a media item from a post is to delete either the post or the media item. This plugin solves that by adding an ‘Unattach’ link below each media file in the Media Library admin list view.
<a href="http://outlandish.com/blog/2011/03/unattach/" rel="nofollow ugc">Plugin by Outlandish</a>

Unattach

Allows detaching images and other media from posts, pages and other content types.

WP Disable Attachment Pages vs Unattach