Temporary WebExtension: after login firefox account. Got xmlhttp.status: 0

I am writing a WebExtension to communicate with a server using XMLHttpRequest.

I load this WebExtension temporarily by about:debugging. It works well if I do not login into my Firefox account. It can get data from the server.

But after logining into my account, it returns “xmlhttp.status: 0” immediately when I trying to do the same thing.

Then I removed all my add-ons, but still I have this problem. I have to refresh Firefox to make my add-on work again.

Any suggestions will be appreciated.

xhr returns “Network request failed” immediately after trying to open connection.

Hmm, could a non-default preference value stored in your Firefox Account Sync data be interfering with XHR requests??

You could try a “before and after” text compare of your prefs.js file (in your currently active profile folder).

Status 0 usually means either the network is offline or the loading of the resource was blocked, for example by tracking protection. Not sure what kind of settings get synced via Firefox Account, but it might sync something in that causes the resource to be blocked.