BandanaManager is not able to store/retrieve custom Java objects anymore

When trying to store/retrieve custom Java objects in Confluence 6.0.0-beta3, the following error occurs:

com.thoughtworks.xstream.converters.ConversionException: XStream error: Class com.simplenia.confluence.plugins.customdashboards.data.DashboardFilterRule has not been whitelisted

I'm a bit surprised to see this change, as it has always been possible to store/retrieve custom Java objects in BandanaManager in the past. Atlassian even mentions this in the documentation: https://developer.atlassian.com/confdev/development-resources/confluence-architecture/confluence-internals/persistence-in-confluence

Bandana is an Atlassian framework for persistence of arbitrary Java objects.

Is this really something you need to change? This is going to break lots of plugins for sure...

Any help/advise would be appreciated.

Cheers,
Remo