Starting with Firefox 70, for security reasons, dedicated and shared worker scripts served with a wrong MIME type will be blocked from loading with
SharedWorker() respectively. The change has been made to the Nightly and early Beta channels while developers are evaluating the compatibility.
The same change has already been made in Firefox 67 to scripts loaded with
importScripts(). Make sure your script files are always served with
Update: We have updated the title and content since this change has been made only to the non-Release channels so far.
Update 2: Adobe Color is known to be broken due to this change.