No referrer

The rel="noreferrer" attribute indicates that the browser should not send a Referer header when following the link. It enhances privacy by allowing users to avoid leaking referrer information when they click on (or prefetch) links to external sites. It also enhances security by preventing the linked page from gaining access to the linking page via the window.opener object.

This module provides a filter which, if enabled for a text format, adds a rel="noreferrer" attribute to all external links in user-generated content. You will probably want to enable the "No referrer" filter on all of your text formats.

This module also adds a rel="noreferrer" attribute to all external links generated by code (e.g. menu module). Note, enabling this setting may have a small negative impact on Drupal 7 site performance because each link will be processed by the theme layer.

The settings page allows site administrators to define a whitelist of domains for which the rel="noreferrer" attribute will not be added.