I have an extension containing a action for an ajax call, which returns a json string. There is also a plugin inserted on a specific page for the user input. The plugin has some settings (via flexform), which I want to get at the ajax call, but I have no idea how.
ajaxCall = PAGE
ajaxCall {
    typeNum = 1000
    config {
        disableAllHeaderCode = 1
        metaCharset = UTF-8
        no_cache = 1
        debug = 0
    }
    10 = USER
    10 {
        userFunc = TYPO3\CMS\Extbase\Core\Bootstrap->run
        vendorName = Vendor
        pluginName = SomePlugin
        extensionName = SomeExtension
        controller = MyController
        action = ajax
        switchableControllerActions {
            MyController {
                1 = ajax
            }
        }
    }
}