Most browsers have safe browsing features that send unknown URLs to a cloud service for verification. I was shocked once to see an S3 presigned URL be accessed

Most browsers have safe browsing features that send unknown URLs to a cloud service for verification. I was shocked once to see an S3 presigned URL be accessed from Russia and India, when I had not shared it yet. It turned out to be Google safe browsing service (this case was several years ago and was verified with Google; I don’t know where URLs are investigated these days). Another possible culprit is browser extensions. If you give an extension permission to a URL or page content, you have no idea if or where it’s sending it. Some extensions intentionally send URLs to cloud services for benign purposes (ex: Microsoft safe browsing extension for non-MS browsers).