WebExtensions content script won't be attached to some CSP pages

Add-ons Development
#1

WebExtensions content script won’t be attached to some web pages when the page specifies Content Security Policy.

Is this by design? A bug?
Or, am I missing something?

sample content.js:

"use strict";
{
  console.log("content script attached");
}

manifest.json:

{
  "applications": {
    "gecko": {
      "id": "webExtTest@asamuzak.jp"
    }
  },
  "content_scripts": [
    {
      "matches": ["<all_urls>"],
      "js": ["./content.js"],
      "run_at": "document_end"
    }
  ],
  "manifest_version": 2,
  "name": "WebExtensions test",
  "permissions": [
    "<all_urls>",
    "activeTab"
  ],
  "version": "0.0.1"
}

https://bugzilla.mozilla.org/
https://discourse.mozilla-community.org/c/add-ons
Works

https://addons.mozilla.org/en-US/firefox/
Doesn’t work.
CSP error is logged in console, too.

#2

Content scripts are blocked on addons.mozilla.org -> https://bugzilla.mozilla.org/show_bug.cgi?id=1310082

#3

Thanks.