Nothing has changed in ApiQuerySiteInfo since 1.32.0-wmf.18.

On testwiki,

hphpd> =$wgContLang->getNamespaceAliases();
=$wgContLang->getNamespaceAliases();
Array
(
    [Judgement] => 810
    [Judgement_talk] => 811
)

hphpd> =$wgContLang->getNamespaces();
=$wgContLang->getNamespaces();
Array
(
    [-2] => "Media"
    [-1] => "Special"
    [0] => ""
    [1] => "Talk"
    [2] => "User"
    [3] => "User_talk"
    [4] => "Wikipedia"
    [5] => "Wikipedia_talk"
    [6] => "File"
    [7] => "File_talk"
    [8] => "MediaWiki"
    [9] => "MediaWiki_talk"
    [10] => "Template"
    [11] => "Template_talk"
    [12] => "Help"
    [13] => "Help_talk"
    [14] => "Category"
    [15] => "Category_talk"
    [90] => "Thread"
    [91] => "Thread_talk"
    [92] => "Summary"
    [93] => "Summary_talk"
    [118] => "Draft"
    [119] => "Draft_talk"
    [460] => "Campaign"
    [461] => "Campaign_talk"
    [710] => "TimedText"
    [711] => "TimedText_talk"
    [828] => "Module"
    [829] => "Module_talk"
    [830] => "SecurePoll"
    [831] => "SecurePoll_talk"
    [866] => "CNBanner"
    [867] => "CNBanner_talk"
    [1198] => "Translations"
    [1199] => "Translations_talk"
    [2300] => "Gadget"
    [2301] => "Gadget_talk"
    [2302] => "Gadget_definition"
    [2303] => "Gadget_definition_talk"
    [2600] => "Topic"
    [5500] => "Newsletter"
    [5501] => "Newsletter_talk"
)

What's defining aliases for namespaces 810 and 811 when those namespaces aren't defined?

Looks like the answer is Jade, due to rEJADe74405d81b4a: Add a namespace alias for "judgement" in English and rEJADdbbe71c83558: Add another namespace alias for the "Judgement_talk" spelling.

Although I'm not immediately seeing what it's doing wrong that's making the aliases be loaded when the extension itself isn't.

I note that trying to visit https://test.wikipedia.org/wiki/Judgement:Foo redirects to https://test.wikipedia.org/wiki/Special:Badtitle/NS810:Foo, to display a bad title error.

It looks like no other extension is defining any namespace aliases via an ExtensionMessagesFiles file, and our localization cache logic is pulling in those files from all extensions whether they're loaded on the wiki or not (because the cache isn't separated per wiki).

Probably the solution is to have Language::getNamespaceAliases() filter out aliases to namespaces that aren't defined on the wiki.

Change 464053 had a related patch set uploaded (by Anomie; owner: Anomie):
[mediawiki/core@master] Language: Don't return aliases to namespaces that don't exist

https://gerrit.wikimedia.org/r/464053

Thanks for the fix and apologies for having invented a non-standard way to provide the namespace aliases…

I think it's more that you just started using a feature that has either never been used or hasn't been used in a long time, so you uncovered a bug.

Change 464053 merged by jenkins-bot:
[mediawiki/core@master] Language: Don't return aliases to namespaces that don't exist

https://gerrit.wikimedia.org/r/464053

Change 464093 had a related patch set uploaded (by Krinkle; owner: Anomie):
[mediawiki/core@wmf/1.32.0-wmf.24] Language: Don't return aliases to namespaces that don't exist

https://gerrit.wikimedia.org/r/464093

Change 464093 merged by jenkins-bot:
[mediawiki/core@wmf/1.32.0-wmf.24] Language: Don't return aliases to namespaces that don't exist

https://gerrit.wikimedia.org/r/464093

Mentioned in SAL (#wikimedia-operations) [2018-10-03T05:24:20Z] <krinkle@deploy1001> Synchronized php-1.32.0-wmf.24/languages/Language.php: T206030 - I985dfa3eb17 (duration: 00m 56s)