.load failed in Firefox > 68

.load failed in Firefox > 68

Hi there, have a problem with jquery .load function. Have an index.html file and try to insert a xyz,html file from subfolder at a certain div position: <script>$("divpos").load("subfolder/xyz.html");</script>

Worked until Firefox 67, but now get in console this:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at file:///C:/Users/name/Documents/00%20MyData/005%20xyz.html. (Reason: CORS request not http)

And: File xyz.html is not loaded!

Changing Firefox parameter privacy.file_unique_origin to false , it worked again . But not sure if setting
privacy.file_unique_origin to false is safe?

Excuse my German-English, and thanks for any ideas to solve my problem.