Set Microsoft Word links to open in new window/tab

The solution for this would be to build a filter on the_content that scans the pasted text for links and adds target="_blank". Actually, you don’t even have to build it yourself, because WP has a built in function to do this. All you have to do is add this line to the functions.php of your theme:

add_filter ('the_content','links_add_target');

Beware that if your theme is updated your functions.php will be replaced and your edit lost. The correct way to circumvent this would be to build a child theme.