API modules can include a `getHelpUrls` function. The url is displayed in multiple places, including within the API help and the API sandbox (if that extension in installed). All such links that point to mediawiki should use `https://www.mediawiki.org/wiki/Special:MyLanguage/Help page` instead of just `https://www.mediawiki.org/wiki/Help page`
A [ codesearch ](https://codesearch.wmflabs.org/search/?q=return%20%27https%3A%5C%2F%5C%2Fwww%5C.mediawiki%5C.org%5C%2Fwiki%5C%2F%5B%5ES%5D&i=fosho&files=&repos=) reveals 19 extensions that add help links without using `Special:MyLanguage` - the search isn't perfect, since it doesn't support negative lookaheads, but it is a starting place, and the scope of //this// task is to fix those identified.
For clarity, the following extensions will be affected:
Uploading patches now, once they are all available for review I will tag the extensions.