duckduckgo · laghee · Oct 14, 2025 · Oct 14, 2025 · Oct 21, 2025 · Oct 21, 2025
@@ -0,0 +1,23 @@
+{
+    "readme": "This config tests that uaChBrands can override navigator.userAgentData.brands",
+    "version": 1,
+    "unprotectedTemporary": [],
+    "features": {
+        "uaChBrands": {
+            "state": "enabled",
+            "exceptions": [],
+            "settings": {
+                "brands": [
+                    {
+                        "brand": "Chromium",
+                        "version": "140"
+                    },
+                    {
+                        "brand": "DuckDuckGo",
+                        "version": "140"
+                    }
+                ]
+            }
+        }
+    }
+}
diff --git a/injected/integration-test/test-pages/ua-ch-brands/config/brands-missing.json b/injected/integration-test/test-pages/ua-ch-brands/config/brands-missing.json
@@ -0,0 +1,13 @@
+{
+    "readme": "This config tests that uaChBrands feature returns early when brands setting is missing (feature is enabled but settings.brands is undefined)",
+    "version": 1,
+    "unprotectedTemporary": [],
+    "features": {
+        "uaChBrands": {
+            "state": "enabled",
+            "exceptions": [],
+            "settings": {
+            }
+        }
+    }
+}
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width">
+    <title>UA CH Brands</title>
+    <link rel="stylesheet" href="../shared/style.css">
+</head>
+<body>
+    <p><a href="../index.html">[Home]</a></p>
+
+    <p>UA CH Brands</p>
+    <ul>
+        <li><a href="./pages/brand-override.html">Brand Override</a> - <a href="./config/brand-override.json">Config</a></li>
+        <li><a href="./pages/brands-missing.html">Brands Missing</a> - <a href="./config/brands-missing.json">Config</a></li>
+    </ul>
+</body>
+</html>
@@ -0,0 +1,103 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width">
+  <title>UA CH Brands - Brand Override</title>
+  <link rel="stylesheet" href="../../shared/style.css">
+</head>
+<body>
+    <script src="../../shared/utils.js"></script>
+    <p><a href="../index.html">[UA CH Brands]</a></p>
+
+    <p>This page verifies that navigator.userAgentData.brands uses the configured brands from the uaChBrands feature settings</p>
+
+    <script>
+        test('Brand override', async () => {
+            const results = [];
+
+            if (navigator.userAgentData && navigator.userAgentData.brands) {
+                const brands = navigator.userAgentData.brands;
+                const brandNames = new Set(brands.map(b => b.brand));
+
+                results.push({
+                    name: 'contains Chromium brand',
+                    result: brandNames.has('Chromium'),
+                    expected: true
+                });
+
+                results.push({
+                    name: 'contains DuckDuckGo brand',
+                    result: brandNames.has('DuckDuckGo'),
+                    expected: true
+                });
+
+                results.push({
+                    name: 'has correct number of brands',
+                    result: brands.length,
+                    expected: 2
+                });
+
+                results.push({
+                    name: 'does not contain Microsoft Edge brand',
+                    result: !brandNames.has('Microsoft Edge'),
+                    expected: true
+                });
+
+                results.push({
+                    name: 'does not contain Microsoft Edge WebView2 brand',
+                    result: !brandNames.has('Microsoft Edge WebView2'),
+                    expected: true
+                });
+
+                if (navigator.userAgentData.getHighEntropyValues) {
+                    try {
+                        const highEntropyValues = await navigator.userAgentData.getHighEntropyValues(['brands']);
+                        if (highEntropyValues.brands) {
+                            const heBrandNames = new Set(highEntropyValues.brands.map(b => b.brand));
+                            results.push({
+                                name: 'high entropy contains Chromium',
+                                result: heBrandNames.has('Chromium'),
+                                expected: true
+                            });
+                            results.push({
+                                name: 'high entropy contains DuckDuckGo',
+                                result: heBrandNames.has('DuckDuckGo'),
+                                expected: true
+                            });
+
+                            results.push({
+                                name: 'high entropy does not contain Microsoft Edge',
+                                result: !heBrandNames.has('Microsoft Edge'),
+                                expected: true
+                            });
+
+                            results.push({
+                                name: 'high entropy does not contain Microsoft Edge WebView2',
+                                result: !heBrandNames.has('Microsoft Edge WebView2'),
+                                expected: true
+                            });
+                        }
+                    } catch (error) {
+                        results.push({
+                            name: 'getHighEntropyValues works',
+                            result: false,
+                            expected: true
+                        });
+                    }
+                }
+            } else {
+                results.push({
+                    name: 'navigator.userAgentData.brands available',
+                    result: false,
+                    expected: true
+                });
+            }
+
+            return results;
+        });
+
+        renderResults();
+    </script>
+</body>
+</html>
diff --git a/injected/integration-test/test-pages/ua-ch-brands/pages/brands-missing.html b/injected/integration-test/test-pages/ua-ch-brands/pages/brands-missing.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width">
+  <title>UA CH Brands - Brands Missing</title>
+  <link rel="stylesheet" href="../../shared/style.css">
+</head>
+<body>
+    <script src="../../shared/utils.js"></script>
+    <p><a href="../index.html">[UA CH Brands]</a></p>
+
+    <p>This page verifies that when brands setting is missing/null/empty, the feature returns early and original brands are preserved</p>
+
+    <script>
+        test('Feature returns early when brands missing', async () => {
+            const results = [];
+
+            if (navigator.userAgentData && navigator.userAgentData.brands) {
+                // When brands setting is missing, the feature returns early in init()
+
+                const brands = navigator.userAgentData.brands;
+
+                // Verify brands still works normally
+                results.push({
+                    name: 'brands array exists and has content',
+                    result: Array.isArray(brands) && brands.length > 0,
+                    expected: true
+                });
+
+                // Verify getHighEntropyValues also works and returns matching values
+                if (navigator.userAgentData.getHighEntropyValues) {
+                    try {
+                        const highEntropyValues = await navigator.userAgentData.getHighEntropyValues(['brands']);
+                        const heBrands = highEntropyValues.brands;
+
+                        if (heBrands) {
+                            // Both should return the same unwrapped values
+                            const brandsStr = JSON.stringify(brands);
+                            const heBrandsStr = JSON.stringify(heBrands);
+
+                            results.push({
+                                name: 'getHighEntropyValues and direct access return matching values',
+                                result: brandsStr === heBrandsStr,
+                                expected: true
+                            });
+                        }
+                    } catch (error) {
+                        results.push({
+                            name: 'getHighEntropyValues works',
+                            result: false,
+                            expected: true
+                        });
+                    }
+                }
+            } else {
+                results.push({
+                    name: 'navigator.userAgentData.brands available',
+                    result: false,
+                    expected: true
+                });
+            }
+
+            return results;
+        });
+
+        renderResults();
+    </script>
+</body>
+</html>
@@ -0,0 +1,36 @@
+import { test, expect } from '@playwright/test';
+import { ResultsCollector } from './page-objects/results-collector.js';
+
+test('UA CH Brands override', async ({ page }, testInfo) => {
+    const collector = ResultsCollector.create(page, testInfo.project.use);
+    await collector.load(
+        '/ua-ch-brands/pages/brand-override.html',
+        './integration-test/test-pages/ua-ch-brands/config/brand-override.json',
+    );
+    const results = await collector.results();
+
+    for (const key in results) {
+        for (const result of results[key]) {
+            await test.step(`${key}: ${result.name}`, () => {
+                expect(result.result).toEqual(result.expected);
+            });
+        }
+    }
+});
+
+test('UA CH Brands when brands missing', async ({ page }, testInfo) => {
+    const collector = ResultsCollector.create(page, testInfo.project.use);
+    await collector.load(
+        '/ua-ch-brands/pages/brands-missing.html',
+        './integration-test/test-pages/ua-ch-brands/config/brands-missing.json',
+    );
+    const results = await collector.results();
+
+    for (const key in results) {
+        for (const result of results[key]) {
+            await test.step(`${key}: ${result.name}`, () => {
+                expect(result.result).toEqual(result.expected);
+            });
+        }
+    }
+});
@@ -10,6 +10,7 @@ export default defineConfig({
                 'integration-test/duckplayer-remote-config.spec.js',
                 'integration-test/harmful-apis.spec.js',
                 'integration-test/windows-permissions.spec.js',
+                'integration-test/ua-ch-brands.spec.js',
                 'integration-test/broker-protection-tests/**/*.spec.js',
                 'integration-test/breakage-reporting.spec.js',
                 'integration-test/duck-ai-data-clearing.spec.js',

@@ -26,6 +26,7 @@ const otherFeatures = /** @type {const} */ ([
     'harmfulApis',
     'webCompat',
     'windowsPermissionUsage',
+    'uaChBrands',
     'brokerProtection',
     'performanceMetrics',
     'breakageReporting',
@@ -68,6 +69,7 @@ export const platformSupport = {
         ...baseFeatures,
         'webTelemetry',
         'windowsPermissionUsage',
+        'uaChBrands',
         'duckPlayer',
         'brokerProtection',
         'breakageReporting',

@@ -0,0 +1,91 @@
+import ContentFeature from '../content-feature';
+
+export default class UaChBrands extends ContentFeature {
+    constructor(featureName, importConfig, args) {
+        super(featureName, importConfig, args);
+
+        this.cachedBrands = null;
+        this.originalBrands = null;
+    }
+
+    init() {
+        const configuredBrands = this.getFeatureSetting('brands');
+
+        if (!configuredBrands || configuredBrands.length === 0) {
+            this.log.info('No client hint brands correctly configured, feature disabled');
+            return;
+        }
+        this.shimUserAgentDataBrands();
+    }
+
+    /**
+     * Override navigator.userAgentData.brands to match the Sec-CH-UA header
+     */
+    shimUserAgentDataBrands() {
+        try {
+            // @ts-expect-error - userAgentData not yet standard
+            if (!navigator.userAgentData || !navigator.userAgentData.brands) {
+                return;
+            }
+
+            if (!this.originalBrands) {
+                // @ts-expect-error - userAgentData not yet standard
+                this.originalBrands = [...navigator.userAgentData.brands];
+            }
+
+            if (this.cachedBrands) {
+                this.applyBrandsOverride(this.cachedBrands);
+                return;
+            }
+
+            const mutatedBrands = this.applyBrandMutations();
+
+            if (mutatedBrands) {
+                this.cachedBrands = mutatedBrands;
+                this.applyBrandsOverride(mutatedBrands);
+            }
+        } catch (error) {
+            this.log.error('Error in shimUserAgentDataBrands:', error);
+        }
+    }
+
+    /**
+     * Apply brand mutations using the configured brands from feature settings
+     * @returns {Array<{brand: string, version: string}>|null} - Configured brands or null if no changes
+     */
+    applyBrandMutations() {
+        const configuredBrands = this.getFeatureSetting('brands');
+
+        if (!configuredBrands || configuredBrands.length === 0) {
+            this.log.info('No CH brands configured, skipping mutations');
+            return null;
+        }
+
+        this.log.info('Applying configured brands:', configuredBrands);
+        return configuredBrands;
+    }
+
+    /**
+     * Apply the brand override to navigator.userAgentData.brands
+     * @param {Array<{brand: string, version: string}>} newBrands - Brands to apply
+     */
+    applyBrandsOverride(newBrands) {
+        // @ts-expect-error - userAgentData not yet standard
+        const proto = Object.getPrototypeOf(navigator.userAgentData);
+
+        this.wrapProperty(proto, 'brands', {
+            get: () => newBrands,
+        });
+
+        if (proto.getHighEntropyValues) {
+            this.wrapMethod(proto, 'getHighEntropyValues', async (originalFn, ...args) => {
+                // @ts-expect-error - userAgentData not yet standard
+                const result = await originalFn.apply(navigator.userAgentData, args);
+                if (args[0] && args[0].includes('brands')) {
+                    result.brands = newBrands;
+                }
+                return result;
+            });
+        }
+    }
+}