diff --git a/Library/Homebrew/cask/artifact/abstract_artifact.rb b/Library/Homebrew/cask/artifact/abstract_artifact.rb
index 25b6f02833..14d203ee4b 100644
--- a/Library/Homebrew/cask/artifact/abstract_artifact.rb
+++ b/Library/Homebrew/cask/artifact/abstract_artifact.rb
@@ -99,7 +99,12 @@ module Cask
         description = key ? "#{stanza} #{key.inspect}" : stanza.to_s
 
         # backward-compatible string value
-        arguments = { executable: arguments } if arguments.is_a?(String)
+        arguments = if arguments.is_a?(String)
+          { executable: arguments }
+        else
+          # Avoid mutating the original argument
+          arguments.dup
+        end
 
         # key sanity
         permitted_keys = [:args, :input, :executable, :must_succeed, :sudo, :print_stdout, :print_stderr]
diff --git a/Library/Homebrew/test/cask/artifact/abstract_artifact_spec.rb b/Library/Homebrew/test/cask/artifact/abstract_artifact_spec.rb
new file mode 100644
index 0000000000..24e35e969d
--- /dev/null
+++ b/Library/Homebrew/test/cask/artifact/abstract_artifact_spec.rb
@@ -0,0 +1,29 @@
+# typed: false
+# frozen_string_literal: true
+
+describe Cask::Artifact::AbstractArtifact, :cask do
+  describe ".read_script_arguments" do
+    let(:stanza) { :installer }
+
+    it "accepts a string, and uses it as the executable" do
+      arguments = "something"
+
+      expect(described_class.read_script_arguments(arguments, stanza)).to eq(["something", {}])
+    end
+
+    it "accepts a hash with an executable" do
+      arguments = { executable: "something" }
+
+      expect(described_class.read_script_arguments(arguments, stanza)).to eq(["something", {}])
+    end
+
+    it "does not mutate the original arguments in place" do
+      arguments = { executable: "something" }
+      clone = arguments.dup
+
+      described_class.read_script_arguments(arguments, stanza)
+
+      expect(arguments).to eq(clone)
+    end
+  end
+end