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:
[X] Echo (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Echo/+/532521/)
[X] PageAssessments (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/PageAssessments/+/532524/)
[X] PageViewInfo (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/PageAssessments/+/532524/)
[X] Checkuser (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/CheckUser/+/532526/)
[] GeoData (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/GeoData/+/532527/)
[X] MachineVision (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/MachineVision/+/532528/)
[] RegexBlock (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/RegexBlock/+/532529/)
[X] TimedMediaHandler (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/TimedMediaHandler/+/532530/)
[] Wikibase (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Wikibase/+/532531/)
[X] ApiFeatureUsage (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/ApiFeatureUsage/+/532532/)
[X] BetaFeatures (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/BetaFeatures/+/532533/)
[] Favorites (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Favorites/+/532534/)
[X] Flow (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Flow/+/532535/)
[X] Jade (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/Jade/+/532536/)
[X] MobileFrontEnd (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/MobileFrontend/+/532538/)
[X] Ores (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/ORES/+/532539/)
[X] TemplateData (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/TemplateData/+/532540/)
[X] TextExtracts (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/TextExtracts/+/532541/)
[] UploadWizard (https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/UploadWizard/+/532542/)