There has been a bug in Firefox affecting add-ons which make use of Content Security Policy (CSP) to modify headers. The problem is that when using multiple of such add-ons it is unclear which add-on "wins". In other words: An example Examples of add-ons affected are uBlock Origin, uMatrix, Privacy Badger, CanvasBlocker and HTTPS Everywhere. A related bug report was opened about 2 years ago, among the participants in that discussion were @gorhill and Giorgio Maone (the Noscript author). There is also a lengthy discussion on gHacks-user.js for which the incomparable Thorin-Oakenpants assigned the "needs Jesus" label. Now finally a patch has landed in Firefox Nightly which fixes that bug. The author of this patch demonstrated in this post how to test the different behavior of Firefox stable and Firefox Nightly. Note that Chromium-based browsers are not affected. However, in the discussion of that bug it was mentioned that those browsers don't deal with those situations in an optimal way, either. Anyway, the fix will be available in Firefox 77 to be released on 2020-06-02. So Thorin-Oakenpants will soon be able to alter his label to "Jesus was listening".