Important: #81899 - Backend AJAX routes use "&route=/ajax/" instead of "ajaxId" parameter

See Issue #81899


The TYPO3 Backend uses AJAX calls by calling routes with the &route=/ajax/* GET/POST parameter now instead of the "&ajaxId" GET/POST parameter.

Although this is not a breaking change, some PHP code might rely on GET/POST parameters being set, and must check for the route parameter instead.