From https://www.mediawiki.org/wiki/Phabricator/Help#Creating_your_account I followed the link "Connect your Wikimedia SUL and LDAP accounts to a single Phabricator username!" It worked great and called up OAuth for confirmation.
But the Phabricator "Confirm MediaWiki Account Link" form for the second step has a bogus link. It shows
Confirm the link with this MediaWiki account. This account will be able to log in to your Phabricator account.
MediaWiki Account · 14576418
That URL is garbled and results in 'Bad title'
- The space between "SPage" and "(WMF)" is represented as a + (OK), but then is getting URL-encoded as %2B, which is bad.
- The parentheses are double-URL-encoded -- '(' represented as %28 is OK, but then translating the '%' to produce %2528 is garbage.
- index.php?title isn't necessary for a straight title with no query parameters.
https://www.mediawiki.org/wiki/User:SPage_(WMF) is what you want and all you need here.
I confirmed anway and now I see the same bad URL on the https://phabricator.wikimedia.org/settings/panel/external/ page under "MediaWiki OAuth1 Account"