Forms rendered by the HubSpot form embed codes are updating.Two changes will be occurring. Most accounts and forms should not expect to have any issues.
Additionally our forms embed script will no longer attach internal dependencies to the window.hubspot,window.hbspt, window.HSFR properties. While these dependencies were required for the internal functionality of HubSpot forms, their attachment to a window property made them available for other scripts on the page. In the unlikely event your code relied on these dependencies, you will need to update any form related custom code to rely on their own dependencies.
There isn't a way to test right now. The jist though is, if you followed what's in the documentation, you're fine. You're basically just affected if you specifically wrote custom code that relied on data-react-id, or wrote custom code relying on undocumented window object data. The vast majority of developers would not rely on the window object data, as it was undocumented, and you needed to know that data was there.