TYPO3 Core

If you use f:form in a widget and add some inputs, these (property based or name based) inputs are not prefixed correctly. This leads to validation errors after submitting the form, as the values cannot be recognized due to the missing prefix.

You can circumvent the problem by using fieldNamePrefix attribute on the f:form viewhelper, but if you do so, the form fields are no longer added to the trusted properties.

So in fact there are two issues to solve:
1) properly prefix the viewhelpers when in widget context
2) allow multi-dimensional fieldname prefix in MvcPropertyMappingConfigurationService->generateTrustedPropertiesToken()