ConfirmPasswordController doesn't exist after upgrade from Laravel 5.8 to 6.2
Laravel made the following additions and modifications from versions v6.0.0 to v6.2.0.
A app/Http/Controllers/Auth/ConfirmPasswordController.php
M app/Http/Controllers/Auth/ForgotPasswordController.php
M app/Http/Controllers/Auth/ResetPasswordController.php
M app/Http/Kernel.php
M config/auth.php
M resources/lang/en/validation.php
Please make sure these changes are in your Laravel instance though it sounds like they now are. You can see the diff of v6.0.0 to v6.2.0 here. If you need to see v5.8.0 changes through 6.2.0, please go here.