In this article I read, that using
<a href="" target="blank"> is related to some security issues. They recommend
How do I implement this in my WP-Installation? Which file is the relevant one? Thank you.
This function is used to filter through the various input data just before saving it, e.g.
Since 5.2 the following improvements are made:
There are open tickets to further refine it, e.g.
If you have some custom user input that allows external links, then you could use:
$text = wp_targeted_link_rel( $text );
to handle it.
The default relation values
'noopener noreferrer' are also filterable through the
"Wich file is the relevant one" = All files that allow user generated content to be viewed.
You have to change hook into the_content to change the URLs and add noopener
There is a great answer here: How to add nofollow on all external links without plugin? (and here: A plugin for having rel="nofollow" in posts? ) you should look into.