Firefox clipboard: test whether the content is same-origin before attempting read() or readText()?

A web app allows copying and pasting objects between dialogs. It stores JSON in the clipboard and reads it via JavaScript when Ctrl+V is pressed.

Pasting works fine in Chrome and Firefox when the clipboard actually contains the expected, same-origin JSON. But when the clipboard contains cross-origin content from different application, Firefox pops up a “Paste” dialog the breaks keyboard focus and is generally annoying.

The paste dialog is a security measure according to https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/read#browser_compatibility:

A paste prompt is displayed when the clipboard is read. If the
clipboard contains same-origin content, the prompt is suppressed.

Is it possible to know the clipboard origin before attempting an operator that will trigger the dialog? The web app doesn’t need to read data from a different origin. I’d like to avoid the annoying dialog.