I am exposing a service using a site but facing some issues with the guest user access for object records. While inserting a record, I am getting 'insufficient access rights on cross-reference id' error. I am using master-detail relationships between objects. I checked all the permissions, sharing settings added to the guest user.
I have created a sharing rule on the parent object to provide read access to the guest user but after providing access also, I am getting the cross-reference entity error. I am getting this issue after the winter'21 release. In Winter'21, the 'Secure guest user record access' setting is by default enabled & can't be changed. I think, this is the issue of the error but I have no idea what I am missing to share records with the guest user.
Note:- I can't change the sharing setting in the Apex class.