Last modified: 2014-02-12 23:35:37 UTC
Similar to how $wgNoFollowLinks, $wgNoFollowNsExceptions, and $wgNoFollowDomainException can be used to set rel="nofollow" on certain external links, there should be a complimentary set of config options to set rel="noreferrer". A discussion is ongoing on enwiki about adding noreferrer to external links for privacy reasons (http://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#noreferrer_for_Wikipedia). This will give them the software option of doing so if they decide. Patch soon to come.
https://gerrit.wikimedia.org/r/46790
A quick note. I do *not* agree/disagree with the actual usage of this on enwiki (or any other WMF wiki). I just think it'd be a good feature to add if enwiki or somebody decides they want to add blanket noreferrer to their external links, which may be desirable in private wikis.