Wikimedia Bugzilla is closed!

As in bug 60218. Go to [[mw:Special:ApiSandbox]]:
* action=flow
* page= page you want to blank, one that isn't a Flow board.
* params={"topic_list": {"topic": "Topic!", "content": "Content!"}}
* token=Flow token from API (request tokens type 'flow'), +\ if you're logged out

Press Make request, and the page will be replaced with the string: "This talk
page has been taken over by a
[https://www.mediawiki.org/wiki/Special:MyLanguage/Flow_Portal Flow board]."
The API request returns success and includes the chunk of HTML for the new topic.

But the page isn't a Flow board! The API request should fail.
onPerformAction checks isTalkpageOccupied but returns true if it isn't, and maybe the API should be checking too before it calls ensureFlowRevision().