Trello and Custom Chrome Extension

Hi there,
We are using a custom Google Chrome extension to add some custom buttons under the “ADD TO CARD” section on the right of an open card.
These custom buttons opens a modal and adds some functionality that interacts via an API with our internal time/project management functionality.
Late last week and early this week users users are unable to view the modal that opens after clicking a custom button. It just loads the loader gif.
In the Chrome console, it shows the following:

Access to XMLHttpRequest at '' from origin '' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: The 'Access-Control-Allow-Origin' header has a value 'null' that is not equal to the supplied origin.

Please advise on what has changed recently and if we can correct this on our custom Chrome extension?
Thank you

Hey Yatish,

I’ll share this info with our team. Unfortunately, this is unlikely to be something that we’re able to fix as the DOM isn’t an officially supported interface. It is likely that we introduced a new code path that is required by a recently launched feature or underlying architectural change. Since the DOM is not an officially supported API, our team does not ensure that breaking changes aren’t introduced.

Our recommendation for building integrations that extend Trello continues to be that Power-Ups are the best platform to use to extend Trello’s functionality. We do our best to keep it stable and not introduce breaking changes.