The Admin Classic Bundle provides a Backend UI for Pimcore. `AdminBundle\Security\PimcoreUserTwoFactorCondition` introduced in v11 disable the two factor authentication for all non-admin security firewalls. An authenticated user can access the system without having to provide the two factor credentials. This issue has been patched in version 1.2.2.
https://patch-diff.githubusercontent.com/raw/pimcore/admin-ui-classic-bundle/pull/345.patch
https://github.com/pimcore/admin-ui-classic-bundle/security/advisories/GHSA-9wwg-r3c7-4vfg
https://github.com/pimcore/admin-ui-classic-bundle/pull/345
https://github.com/pimcore/admin-ui-classic-bundle/commit/e412b0597830ae564a604e2579eb40e76f7f0628