This is a notice that on Tuesday, Jan 28th between 21:00-22:00 UTC (1-2pm PST) Wikimedia Foundation will release critical security updates for current and supported branches of the MediaWiki software and extensions. Downloads and patches will be available at that time, with the git repositories updated soon after. The vulnerable feature is not enabled in MediaWiki by default, however many sites will want to upgrade as soon as the patch is available.