In solidus before versions 2.8.6, 2.9.6, and 2.10.2, there is an bility to change order address without triggering address validations.
This vulnerability allows a malicious customer to craft request data with parameters that allow changing the address of the current order without changing the shipment costs associated with the new shipment.
All stores with at least two shipping zones and different costs of shipment per zone are impacted.
This problem comes from how checkout permitted attributes are structured. We have a single list of attributes that are permitted across the whole checkout, no matter the step that is being submitted.
See the linked reference for more information.
As a workaround, if it is not possible to upgrade to a supported patched version, please use this gist in the references section.