I've created an HTML page while trying out a JavaScript library and am loading both the page and its data source (a JSON file) from local files for now, using file:/// URIs. A week or two ago, when I first tried this, I encountered a "CORS request not http" error, as described [https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp here], when trying to load the JSON file. In my about:config, I set the privacy.file_unique_origin preference to false, after which I was able to load the JSON file successfully. A couple of days ago, though, I started to see the "CORS request not http" error again, and I have seen it every time I have loaded the page since then, despite confirming that privacy.file_unique_origin was still set to false. I've tried several things to try to get that preference to take effect again: resetting privacy.file_unique_origin to true, setting it back to false, and restarting Firefox; reinstalling Firefox; and refreshing Firefox. Screenshots of the error message and the privacy.file_unique_origin preference are attached. I'd appreciate any suggestions of what I should try to get the JSON file:/// resource to load successfully again. Thank you.