Looking at https://www.mediawiki.org/wiki/Extension:SpamBlacklist#Setting_the_blacklist, the local page Mediawiki:Spam-blacklist is taken up by the extension as default list of blacklist, and the English Wikipedia has it over here: https://en.wikipedia.org/wiki/MediaWiki:Spam-blacklist
Now testing the same with API sandbox, for b2old2play.com, which is already blacklisted, as per
\b2old2play\.com\b
in https://en.wikipedia.org/wiki/MediaWiki:Spam-blacklist.
The result is astonishing:
https://en.wikipedia.org/wiki/Special:ApiSandbox#action=spamblacklist&format=json&url=b2old2play.com
{ "spamblacklist": { "result": "ok" } }
The API returned 'OK' even though the URL was blacklisted. Strange ? something similar is happening with my patch : https://gerrit.wikimedia.org/r/#/c/221368/