Be more cautious when parsing charset from file

lib/open_project/file_command_content_type_detector.rb

@@ -90,8 +90,11 @@ module OpenProject
     end
 
     def extract_mime_and_charset(type)
-      mime, charset_param = type.split(";", 2).map(&:strip)
-      charset = charset_param&.match(/\Acharset=(.+)\z/)&.[](1)
+      parts = type.split(";").map(&:strip)
+      mime = parts.first
+      charset = parts.drop(1)
+                     .filter_map { |p| p.match(/\Acharset=([^\s;]+)\z/)&.[](1) }
+                     .first
       charset = nil if charset == "binary"
       [mime, charset]
     end

spec/lib/open_project/file_command_content_type_detector_spec.rb

@@ -99,6 +99,29 @@ RSpec.describe OpenProject::FileCommandContentTypeDetector do
     expect(Open3).to have_received(:capture2).with("file", "-b", "--mime", "--", "--help")
   end
 
+  describe "charset parsing edge cases" do
+    def detect(raw_output)
+      allow(Open3).to receive(:capture2).and_return [raw_output, 0]
+      described_class.new("any").detect
+    end
+
+    it "extracts charset when followed by an extra unknown parameter" do
+      expect(detect("text/plain; charset=utf-8; taste=banana")).to eq(["text/plain", "utf-8"])
+    end
+
+    it "only captures the charset token, not trailing content" do
+      expect(detect("text/plain; charset=utf-8;extra")).to eq(["text/plain", "utf-8"])
+    end
+
+    it "returns nil charset when charset= has no value" do
+      expect(detect("text/plain; charset=")).to eq(["text/plain", nil])
+    end
+
+    it "ignores unrecognised parameters before charset" do
+      expect(detect("text/plain; taste=banana; charset=iso-8859-1")).to eq(["text/plain", "iso-8859-1"])
+    end
+  end
+
   describe "charset detection from real fixture files" do
     let(:utf8_fixture)    { Rails.root.join("spec/fixtures/encoding/utf-8.txt").to_s }
     let(:iso8859_fixture) { Rails.root.join("spec/fixtures/encoding/iso-8859-1.txt").to_s }