TYPO3 Core

To reproduce the bug:

in settings.php

'EXTENSIONS' => [
   'backend' => [
      'loginLogo' => 'fileadmin/user_upload/test.jpg',
   ],
],

in SystemEmail.html, use `<f:image base64="true" src="{typo3.systemConfiguration.backend.loginLogo}" />`

Then, use the "forgot password" link before you log in the backend

It will trigger this exception

Core: Exception handler (WEB): Uncaught TYPO3 Exception: #1375955684: You are not allowed to access the given folder: "_processed_" | TYPO3\CMS\Core\Resource\Exception\InsufficientFolderAccessPermissionsException thrown in file /var/www/html/vendor/typo3/cms-core/Classes/Resource/ResourceStorage.php in line 875. Requested URL: https://test-distrib.ddev.site/typo3/login/password-reset/initiate-reset?loginProvider=1433416747 

A mail sent by EXT:form in a frontend context will work nice as expected.