Unfortunately, CORS or embedding resources from domains hosted on our free hosting is not impossible. This also applies if they use the same base domain or are using the same account.
One workaround could be to migrate your website from a subdomain to a subdirectory. Suppose that right now, you have WordPress on blog.example.com and your HTML site on example.com. You could choose to migrate your WordPress site to example.com/blog/, and have your Javascript code point to that. Since they use the same domain (example.com), you don’t have this limitation.