Recently my MV3 extension stopped working (although it was working before). After some research I found out that injected scripts/CSS fail to load despite they're listed in web_accessible_resources manifest key. These necessary resources are injected by my content script via document.createElement. It's worth noting that this problem only arises if these resources are injected into a page with a local file (file://) opened; there is no problem on http:// pages.

I get net::ERR_BLOCKED_BY_CLIENT error for all injected resources:

Below is "web_accessible_resources" key in my manifest:

...
"web_accessible_resources": [
  {
    "resources": [
      "harviewer/*",
      "connection.js"
    ],
    "matches": [
      "<all_urls>"
    ]
  }
],
...

AFAIU it is correct, otherwise I'd get another error message like this:

"Allow access to file URLS" checkbox is checked for the extension:

I have no adblock-like extensions installed. Also I've tried to clear browser cache, with no luck.

So is it a bug or a feature? The current Chrome Dev docs don't mention such behaviour.

I've made a MCVE that reproduces the problem.