MediaWiki:Apihelp-createapage-upload-example-1

Upload an image from an infobox in the Special:CreatePage interface using the custom CreatePageImageUploadForm PHP class; requires various values to be set in the WebRequest, such as the actual uploadable file data, so merely accessing a URL like this won't work on its own, obviously. Really, the only thing that should be using this endpoint is Special:CreatePage, and hopefully in the future we can have that use the "regular" core JS API for file uploads (patches welcome!).