The API on enwiki is now giving fatal errors when the special value "max" is set for the limit parameter of various modules (I've tried prop=categories, revisions, and templates quickly, and all three had the problem). The error message is "Exception Caught: Internal error in ApiResult::setElement: Attempting to add element categories=500, existing value is 500".
In my local installation of Mediawiki, this error occurs with r69776 and does not occur with r69775. I haven't yet attempted to see what exactly in that 1334-line diff might have broken things.
Version: 1.17.x
Severity: critical
URL: http://en.wikipedia.org/w/api.php?action=query&cllimit=max&format=yamlfm&prop=categories&titles=Test