I have been messing around building a Chrome extension and am fetching some resources using good ol’ XMLHttpRequest(). At least I was trying to do so and instead was getting an epic fail.

I am using the google developer debugger to test (tutorial) and saw the following error in the console.

Example:

Origin [YOUR_RESOURCE_NAME] is not allowed by Access-Control-Allow-Origin Error.

I thought I had configured my manifest.json file with the correct permissions.

...snip...
  "permissions" : [
    "https://*.domain.com"
  ],
...snip...

Turns out I was simply missing the trailing slash /.

...snip...
  "permissions" : [
    "https://*.domain.com/"
  ],
...snip...

Hope that helps someone.