diff --git a/pkgs/applications/networking/browsers/firefox/packages.nix b/pkgs/applications/networking/browsers/firefox/packages.nix
index ad8a3e282f18..a22221d479a8 100644
--- a/pkgs/applications/networking/browsers/firefox/packages.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages.nix
@@ -10,10 +10,10 @@ rec {
 
   firefox = common rec {
     pname = "firefox";
-    ffversion = "65.0.2";
+    ffversion = "66.0";
     src = fetchurl {
       url = "mirror://mozilla/firefox/releases/${ffversion}/source/firefox-${ffversion}.source.tar.xz";
-      sha512 = "2qai7krlc5whsbnwbn67d63lbm7j8mnx8nq0cw44j9nf5gnqx80afqcs08705xlf0n350xa5iif6b9m4nw0jwikps25cirwavrra348";
+      sha512 = "1izxikivz0jb8kzq4cd040a70s3j83nw324yvvbmi7g808s7s6b8ljia5allbrkqcgrvrx3rq4w09kwffwmwd43jxgc1bfl8af3v8d9";
     };
 
     patches = [