I got this somehow. Note that Special: prefix in action= is missing.
<form id='mw-newentity-form1' action='/wiki/NewItem' method='post' enctype='application/x-www-form-urlencoded' class='mw-htmlform-ooui oo-ui-layout oo-ui-formLayout'>
This was achieved by trying to create an item with language=zh-cn, label=User:... (which is rejected by "Links to userpages" on Wikidata).
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Open | None | T96040 Wikibase special pages (tracking) | |||
| Duplicate | None | T123621 #mw-newentity-form1 sometimes has incorrect action attribute |
I can reproduce this as described. Works in all languages. Simply go to https://www.wikidata.org/wiki/Special:NewItem?label=User:Test and try to submit the form twice. I believe this is a bug in the HTMLForm class.