When there is an approval request from EJBCA 5.x or earlier, and there is an attempt to list or view it, a deserialization error occurs:

java.io.InvalidClassException: org.ejbca.core.model.ra.UserDataVO; incompatible types for field type

This affects both the "Approve Actions" list in the AdminWeb and the "Manage Requests" page in the RA web.

This happens because there was a serialization incompatible change in UserDataVO. The type field was changed from int type to EndEntityType type.

Adding an issue so it becomes searchable at least. Given that nobody has complained since 6.0.0 was released, it does not seem to be important to fix.