2020-09-26: MediaWiki 1.35.0 upgrade
MediaWiki is the software that runs Wikipedia and thousands of other wiki sites. Yesterday they released the brand new 1.35.0 version.
It is a bundled with a new VisualEditor extension as well as lots of security fixed.
Head over to https://www.mediawiki.org/wiki/Download to fetch the latest release.
Don't forget to read the release notes https://mediawiki.org/wiki/Release_notes/1.35
A note on upgrading
I've done the upgrade myself, and though fairly straight-forward I suggest you start fresh and move back images/*, LocalSettings.php and then re-install any plugins you want to use. Some are not compatible with the new MediaWiki version, and others will need updates to work.
Running on Apache
In order for the VisualEditor to work properly on Subpages you need to add
AllowEncodedSlashes NoDecode to your vhost config.