When using the chrome.downloads.onCreated function, the callback function provided is being called repeatedly with all downloads in the users download history which can be found at chrome://downloads/. Based off documentation (and common sense) this should only fire once when a new download is created.
I have searched extensively about this issue and have come across one short thread from 2014. I am not sure how to reproduce the issue as it happens infrequently or what the best way to solve it is.
chrome.downloads.onCreated.addListener(download => {
console.log("GOT DOWNLOAD");
href = download.finalUrl;
message = {message: "businessHref",href: href};
messageContentScript(message);
});