Manual:$wgExternalLinkTarget/de-formal

Details
Set a default target for external links. If set to e.g. "_blank", this will also set the "noreferrer" and "noopener" link rel to prevent the attack described at https://mathiasbynens.github.io/rel-noopener/. Some older browsers may not support these link attributes, hence setting  to   may represent a security risk to some of your users.

Add the following entry to file in order to open external links in a new window / tab.

If the value is set to false, then no target attribute is used with external links (This behavior is the same as ).