Frontend user

The frontend.user frontend request attribute provides the \TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication object.

Example:

use TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication;

/** @var FrontendUserAuthentication $frontendUserAuthentification */
$frontendUserAuthentification = $request->getAttribute('frontend.user');
$frontendUserAuthentification->fetchGroupData($request);