=== Error ===
Request URL: <https://www.mediawiki.org/wiki/Special:MyLanguage/Wikipedia:Copyrights>
Request ID: `XSYCOgpAAEYAAB1609YAAAAG`
```name=message
MWException: Can't determine talk page associated with interwiki link
```
```name=trace,lines=10
#0 /srv/mediawiki/php-1.34.0-wmf.13/includes/Title.php(1549): NamespaceInfo->getTalkPage(Title)
#1 /srv/mediawiki/php-1.34.0-wmf.13/includes/skins/Skin.php(282): Title->getTalkPage()
#2 /srv/mediawiki/php-1.34.0-wmf.13/includes/skins/Skin.php(164): Skin->preloadExistence()
#3 /srv/mediawiki/php-1.34.0-wmf.13/skins/Vector/includes/SkinVector.php(68): Skin->initPage(OutputPage)
#4 /srv/mediawiki/php-1.34.0-wmf.13/includes/skins/SkinTemplate.php(216): SkinVector->initPage(OutputPage)
#5 /srv/mediawiki/php-1.34.0-wmf.13/includes/OutputPage.php(2580): SkinTemplate->outputPage()
#6 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(891): OutputPage->output(boolean)
#7 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(903): MediaWiki->{closure}()
#8 /srv/mediawiki/php-1.34.0-wmf.13/includes/MediaWiki.php(515): MediaWiki->main()
#9 /srv/mediawiki/php-1.34.0-wmf.13/index.php(42): MediaWiki->run()
#10 /srv/mediawiki/w/index.php(3): require(string)
```
=== Impact ===
Raised rates of HTTP 500 and MediaWiki exceptions.
Use sees:
{F29732578}
=== Notes ===
New in 1.34-wmf.14. The same url returns non-fatal on wikis running the previous deployment version, e.g. <https://meta.wikimedia.org/wiki/Special:MyLanguage/Wikipedia:Copyrights> shows the red-link page for a page that could be named "Wikipedia:Copyrights".
{F29732586}
Although it is also broken because this url either redirect or display a form on the special page. Instead, it is becoming an illegal way to view a page at a strange url. In particular, because it not a valid title to create. Because viewing the page normally would redirect to en.wikipedia.org. This should probably display a (localised) error message instead on an HTTP 40xx response, but returning an uncached HTTP 50x response is a regression.
This is very likely caused by the Title/NamespaceInfo refactoring, as such tagging Core Platform and CC-ing @daniel.