TinyMCE detect remote image dragged-in or uploaded

As documented, TinyMCE allows uploading images automatically: one defines an endpoint (images_upload_url), which is expected to upload the image and return the location for TinyMCE to use in markup.

However, when pasting, dragging or inserting an image from a URL — for example, https://somecdn.com/image.png — TinyMCE will simply embed the image tag with the somecdn.com source, instead of sending the URL to images_upload_url to be uploaded.

I've scoured through the docs here and haven't found any way to configure TinyMCE to do this. Is there a method I can override in order to upload images from URLs as well as local image uploads?

Summary

To clarify:

• Current behavior with local image dragged in: TinyMCE sends the image to the URL specified in images_upload_url, then embeds the source returned.
• Current behavior with remote image dragged in: TinyMCE embeds the remote image, sourced with its remote URL.
• Desired behavior with remote image dragged in, similar to well established products like Microsoft's GroupMe: TinyMCE sends the image URL to the URL specified in images_upload_url, then embeds the source returned. I can figure out how to upload the URL & manually embed the image in TinyMCE, but I need to know what event to intercept to get the dragged-in image URL!

With some tinkering, I was able to figure out how to handle remote images in TinyMCE!

As I'm using TinyMCE with React, I added an onDrop event:

<Editor
    onDrop={onDrop}

And here is my method implementation, with comments:

const onDrop = useCallback((e) => {
const image_url = e.dataTransfer.getData("URL");

/*
    If this is a local file, use the default functionality
    provided using images_upload_url
  */
if (!image_url) {
  return;
}

/*
    Otherwise, intercept the drop event, get the file URL,
    send it to the API to be uploaded, then embed in content
  */

e.preventDefault();

filesAPI
  .upload({
    image_url,
  })
  .then((response) => {
    const { location } = response.data;
    editorRef.current.execCommand(
      "mceInsertContent",
      false,
      `<img src='${location}' />`
    );
  });

return false;
}, []);

The implementation seems to work pretty well! When local images are dropped in, they're processed by the default handler; otherwise the onDrop method uploads the images & inserts a tag with their location. Note that filesAPI in this context is just my app's wrapper around an axios fetch call.