CORS read block on Trello webhook

I working with firebase functions to send POST requests to a callback uri. I created a webhook to listen for changes on a Trello board list. All I want to do is just print the request body to the callback window. Here’s my code:

const functions = require(‘firebase-functions’);
const cors = require(‘cors’)({origin: ‘*’});

// // Create and Deploy Your First Cloud Functions
// //
exports.helloWorld = functions.https.onRequest((request, response) => {
let model = request.body.model;
return cors(request, response, () => {

When I make change to the list on the Trello, I get {} on the callback and the following warning in the chrome console:
Cross-Origin Read Blocking (CORB) blocked cross-origin response with MIME type text/html.

Is anyone experiencing the same issue?

I’m a little bit confused by the setup that you have and when the CORB is coming into play.

Are you able to successfully create the webhook via a POST request to 1/webhooks? Keep in mind that this fires off a HEAD request to the URL that you provide and your server must respond with a 200. You can also list all of the webhooks that you have created via the following API endpoint:

At the point in time you make a change to the list on Trello, Trello’s backend server will send a POST to the URL that you have registered. No frontend code is involved in that request being sent and so the CORB message seems unrelated to the problem you’re experiencing.