On several wikis, an account named "濫用過濾器" has been created on December 17 to perform some technical maintenance on AbuseFilter. This account has sysop rights but it's a system user and no human can use it. The account already existed on wikis where AbuseFilter can perform blocks, which are issued using this account. See T212268 for more information and future plans.
In AbuseFilter, the "控頻" action takes three parameters: count, period and groups. They must now strictly respect the requirements listed on mediawiki.org. A list of broken filters is on Phabricator. If you're familiar with AbuseFilter, please take a look and fix them. 
Changes later this week
The new version of MediaWiki will be on test wikis and MediaWiki.org from January 8. It will be on non-Wikipedia wikis and some Wikipedias from January 9. It will be on all wikis from January 10 (calendar).
Search Platform Office Hours is rescheduled to January 9. Check the details for time and date.
A new beta feature will soon be released on all wikis: The FileExporter. It allows exports of files from a local wiki to Wikimedia Commons, including their file history and page history. Which files can be exported is defined by each wiki's community: Please check your wiki's configuration file if you want to use this feature.
The FileExporter has already been a beta feature on mediawiki.org, meta.wikimedia, deWP, faWP, arWP, koWP and on wikisource.org. After some functionality was added, it's now becoming a beta feature on all wikis. Deployment is planned for January 16. More information can be found on the project page.
Templates with <templatestyles> could not show the difference between the live template and the sandbox version when they were tested. This has now been fixed. <templatestyles> has a new wrapper parameter now. You can use it for selectors like .mw-parser-output <wrapper parameter value> <selector from CSS page>. 
When you see an edit in the recent changes feed or in the history of a page some of them have tags. Some tags are added automatically. You can also add tags manually. Tags for edits that have been added manually can be edited. This didn't work for a little while. This has now been fixed. 
Users who could cause more damage to the wikis if someone took over their account have to have more secure passwords. This includes administrators and other user groups. They can't use passwords that are in a list of common passwords. Accounts with common passwords are easy to take over. The list of common passwords was made longer a few weeks ago and has a different error message. Some user groups have been added to those who can't use common passwords. This is to protect all accounts with user rights that could cause damage. 
You will not be able to edit the wikis for up to 30 minutes on 17 January 07:00 UTC. This is because of a database problem that has to be fixed immediately. You can still read the wikis. Some wikis are not affected. They don't get this message. You can see which wikis are not affected on this page. Most wikis are affected. The time you can not edit might be shorter than 30 minutes. /Johan (WMF)