Firstly: Create file config.js
//
try {
Components.utils.import("resource://gre/modules/addons/XPIProvider.jsm", {})
.eval("SIGNED_TYPES.clear()");
}
catch(ex) {}
You should place this file in C:\Program Files\Mozilla Firefox directory
Secondly: Create file config-prefs.js
pref("general.config.obscure_value", 0);
pref("general.config.filename", "config.js");
You should place this file in C:\Program Files\Mozilla Firefox\defaults\pref
Note!!! If it does not work for you then you should repeat it again! Maybe you need to reinstall your addons after that. Be carefully with file encoding! (UTF-8 and so on).
I am not author of this.
Source: https://forum.mozilla-russia.org/viewtopic.php?id=70326
Author: https://forum.mozilla-russia.org/viewtopic.php?pid=720004#p720004
This metod block install addons on WebExtension API:
Anybody how to fix this problem without delete config.js, config-prefs.js?