I'm on version 11.20.11

I have a model that looks like this:

public class ListModel
    {
        public XhtmlString XhtmlContent { get;set; }
    }
    
    [PropertyDefinitionTypePlugIn]
    public class ListModelProperty : PropertyListBase<ListModel>
    {
    }
    
    public class PropertyListBase<T> : PropertyList<T>
    {
        public PropertyListBase()
        {
            _objectSerializer = this._objectSerializerFactory.Service.GetSerializer("application/json");
        }

        private Injected<ObjectSerializerFactory> _objectSerializerFactory;
        private IObjectSerializer _objectSerializer;

        protected override T ParseItem(string value)
        {
            return _objectSerializer.Deserialize<T>(value);
        }
    }

And a property

[EditorDescriptor(EditorDescriptorType = typeof(CollectionEditorDescriptor<ListModel>))]
 public virtual IList<ListModel> XhtmlStringCollection { get; set; }

If I add a new item to the collection, and add a block to the text field, it gets saved as <div data-contentlink="31223" data-classid="36f4349b-8093-492b-b616-05d8964e4c89" class="epi-contentfragment" contenteditable="false">Test</div> in the list.

This stays fine until i publish the page. When I publish, all attributes but the class are removed from the div, making the block invalid. Is there a way to prevent this?

I would rewrite it to use a contentarea instead, but this is on an existing project, so I don't want to lose data.