Running nixpkgs-update (https://nix-community.org/update-bot/) with UPDATE_INFO: firefox-beta-unwrapped 0 -> 1
attrpath: firefox-beta-unwrapped
Checking auto update branch...
[version] 
[version] skipping because derivation has updateScript
[rustCrateVersion] 
[rustCrateVersion] No cargoHash found
[golangModuleVersion] 
[golangModuleVersion] Not a buildGoModule package with vendorHash
[npmDepsVersion] 
[npmDepsVersion] No npmDepsHash
[updateScript] 
[updateScript] Success
[updateScript] these 2 derivations will be built:
  /nix/store/bcv7mdpjcdvgxh5z3nrai0h4q2y3p2k3-update-firefox-beta-unwrapped.drv
  /nix/store/5zc3k1zrrk07pl9wwg9hinkwrj3yywbv-packages.json.drv
this path will be fetched (871.0 KiB download, 3.2 MiB unpacked):
  /nix/store/qk8lqvsml1crw62qr8307sh4pdbv4z9l-xidel-unstable-2022-11-01
copying path '/nix/store/qk8lqvsml1crw62qr8307sh4pdbv4z9l-xidel-unstable-2022-11-01' from 'https://cache.nixos.org'...
building '/nix/store/bcv7mdpjcdvgxh5z3nrai0h4q2y3p2k3-update-firefox-beta-unwrapped.drv'...
building '/nix/store/5zc3k1zrrk07pl9wwg9hinkwrj3yywbv-packages.json.drv'...

Going to be running update for following packages:
 - firefox-beta-unwrapped-150.0b9

Press Enter key to continue...
Running update for:
Enqueuing group of 1 packages
 - firefox-beta-unwrapped-150.0b9: UPDATING ...
 - firefox-beta-unwrapped-150.0b9: DONE.

Packages updated!

Diff after rewrites:
diff --git a/pkgs/applications/networking/browsers/firefox/packages/firefox-beta.nix b/pkgs/applications/networking/browsers/firefox/packages/firefox-beta.nix
index 6864ad465b89..e91706566e2b 100644
--- a/pkgs/applications/networking/browsers/firefox/packages/firefox-beta.nix
+++ b/pkgs/applications/networking/browsers/firefox/packages/firefox-beta.nix
@@ -10,11 +10,11 @@
 buildMozillaMach rec {
   pname = "firefox-beta";
   binaryName = "firefox-beta";
-  version = "150.0b9";
+  version = "151.0b10";
   applicationName = "Firefox Beta";
   src = fetchurl {
     url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
-    sha512 = "5afa7b27ee38e809717ca02fede9aa5ebe27f9aeb78d7953e7b0790e30edb663bf0053335e42e258b7bf01b8859e6b0a10c23851cf8b495217f954ac41a386d4";
+    sha512 = "b1ce3e452db490c414027e89bbc2df8af208c8292346a8d607b2a9df9a09dd3732b59fff6ba4a8913dfbb260163966cd5d6a8eb2def79bc4026bd087422f9ab1";
   };
 
   meta = {

No auto update branch exists
Old version 150.0b9" not present in staging derivation file with contents: {
  stdenv,
  lib,
  callPackage,
  fetchurl,
  nixosTests,
  buildMozillaMach,
}:

buildMozillaMach rec {
  pname = "firefox-beta";
  binaryName = "firefox-beta";
  version = "151.0b9";
  applicationName = "Firefox Beta";
  src = fetchurl {
    url = "mirror://mozilla/firefox/releases/${version}/source/firefox-${version}.source.tar.xz";
    sha512 = "2d50cbe82dd470ab94148ab57585324ff98950fa25b806065b61ab2f541c795d826f4d9a454225ec798cdcd77dfd453dc50d26f0ccf8bdb5fcdf010244aec45a";
  };

  meta = {
    changelog = "https://www.mozilla.org/en-US/firefox/${lib.versions.majorMinor version}beta/releasenotes/";
    description = "Web browser built from Firefox Beta Release source tree";
    homepage = "http://www.mozilla.com/en-US/firefox/";
    maintainers = with lib.maintainers; [ jopejoe1 ];
    platforms = lib.platforms.unix;
    broken = stdenv.buildPlatform.is32bit;
    # since Firefox 60, build on 32-bit platforms fails with "out of memory".
    # not in `badPlatforms` because cross-compilation on 64-bit machine might work.
    maxSilent = 14400; # 4h, double the default of 7200s (c.f. #129212, #129115)
    license = lib.licenses.mpl20;
    mainProgram = binaryName;
  };
  tests = {
    inherit (nixosTests) firefox-beta;
  };
  updateScript = callPackage ../update.nix {
    attrPath = "firefox-beta-unwrapped";
    versionSuffix = "b[0-9]*";
  };
}