open the file
/wp-admin/admin-header.php
and just after this starting code:
Code: Select all
<?php
/**
* WordPress Administration Template Header
*
* @package WordPress
* @subpackage Administration
*/
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header('Content-Security-Policy: upgrade-insecure-requests');
I did not reversed the problem from where it come out (why the js resource was loaded as http and not https causing the Gutenberg malfunction) and that disappeared after (so i cannot imagine anymore from where it was coming out) when the editor loaded good, after the above applied fix. Seem that once the fix has been applied and you load the editor, and then you update the template, all return to work: maybe it was something wrongly cached that goes fixed automatically.