Firefox File URL Cross-Origin Request Blocked

If you use a web-page that loads resources by file:/// URLs, you may get this error message from Firefox console (open the debugger with F12 key):

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at file:///....... (Reason: CORS request not http)

You can circumvent this in Firefox 112.0.2 by following actions:

• Open a new tab in your Firefox
• In the address line, enter "about:config"
• In the search field on top, enter "security.fileuri.strict_origin_policy"
• Set it to false by using the toggle-button on the right side

Now your page should work. If not, you may have an older Firefox where this was called "privacy.file_unique_origin", or Firefox has disabled the property meanwhile.

Mind that you may have opened a security hole, and you should reset this property to true as soon as possible!