University IT no longer supports installs and upgrades for MediaWiki through the Collaboration Tools Installer and Upgrader. You may continue to run your existing site; however, you are responsible for keeping MediaWiki software for that site up-to-date (see https://www.mediawiki.org/wiki/MediaWiki for more information) and adjusting settings to make it compatible with Stanford's web infrastructure.
As an alternative, University IT offers Confluence, a more supported wiki environment, which allows any authorized user to add, delete, or revise content via a web browser. Confluence is available to Stanford users only.
If you are using MediaWiki as the foundation for a website, a better Stanford option is Stanford Sites, a self-service tool for building and managing websites. Stanford Sites is available to current faculty, staff, and students free of charge.