enablePrivilege

Netscape's signed scripts could request superpowers by name, up to reading the visitor's hard drive, guarded by one dialog box.

In 2026: Dead. The privilege names were grand, UniversalFileRead, UniversalBrowserWrite, UniversalXPConnect, and the security model was a single Yes button. Firefox removed the whole mechanism in 2012. The idea of a page asking for scoped powers came back properly as permission prompts, which at least stopped offering the universe.

Where it came from: Netscape 4 signed script security model, 1997. Removed from Firefox 17 in 2012. Wikipedia ↗

<script language="JavaScript">
// A web page asking politely for the keys to your filesystem.
function readLocalFile() {
  netscape.security.PrivilegeManager
          .enablePrivilege("UniversalFileRead");
  // If the visitor clicked Yes on the warning box, the page
  // could now open files straight off their hard drive.
}
try { readLocalFile(); }
catch (e) { document.write("<p>Refused: " + e + "</p>"); }
</script>