MediaWiki has a LTS release, which receives security updates. Unfortunately most extensions are being developed in current master or maybe latest wmf* branch. That means that downloading an extension from REL1_27 branch (e.g. by using Special:ExtensionDistributor) leaves the user with an outdated and potentially insecure codebase.
Who would benefit
Everyone who wants to use LTS version of MediaWiki and also be sure extensions that work with this version don't have security issues or severe bugs
At least the greater WMF extensions like "WikiEditor", "VisualEditor/Parsoid", "FlaggedRevs", "CategoryTree", ... should get bugfix and security cherry-picks/backports from the current development into REL1_27.
Of course most voluntary, WMF-independent extension developers won't have time/will to do something like this, but maybe we can find a way to help them or at least make them more aware of the LTS release.