Currently most of the browsers are going to deprecate the setters for document.domain method.

Here mentioning about deprecation https://developer.mozilla.org/en-US/docs/Web/API/Document/domain. Please refer this article as well.

However, ckeditor.js or others js are still using document.domain method to set document.domain. Please refer the below link where you will find out the document.domain setter.

We wanted to know your feature plan about document.domain. Means are you planning to use any alternative way or it will still be used in feature? In that case it might be create an issue if setters for document.domain will be deprecated.