> How would you "mark something 'from web'"? This is a file after all. Files can have metadata, and most modern filesystems provide some kind of file attribute

> How would you "mark something 'from web'"? This is a file after all. Files can have metadata, and most modern filesystems provide some kind of file attribute facility. On macOS browsers do exactly what described, setting a file attribute on downloaded files. The user will then be warned when trying to execute the file.