See Issue #96604
The backend module related class method
has been removed.
body of backend modules. This collides with
Content-Security-Policy HTTP headers
and needs to be avoided.
The method has been marked
@internal in late TYPO3 v11 development and
has been removed in v12.
Calling the method in an instance triggers a fatal PHP error.
The extension scanner finds usage candidates as weak match. In general, instances with extensions that come with own backend modules may be affected.