The IP is from the old web server at the McNair Center, suggesting that when I migrated the McNair database into the new wiki, I migrated this issue. (Note that it doesn't appear to be something hardcoded into a .css file, or similar -- I can't find any trace on the filesystem and besides, this wiki was built from a fresh install.)
I found the URLs hardcoded in [[MediaWiki:Common.css]] (it must have been moved with the last big batch of pages and I somehow didn't notice!) but then couldn't edit it! It seems that following [https://www.mediawiki.org/wiki/MediaWiki_1.32/interface-admin Mediawiki 1.32], the rights to edit the interface were separated out, and users now need the editinterface right to change anything in the Mediawiki namespace. So, I went to [[Special:UserRights]] and gave myself permission. Then I fixed edited the page, which changed the look-and-feel of my editor (I have no idea why), removed the consol messages, but left the problem!(even after ctrl-shift-r cache flush on Chrome).
===Install VSFTPD===