fix: split stealth init scripts by browser engine and add Firefox stealth

The stealth system previously injected all 12 init scripts unconditionally
into every browser engine. Chromium-specific scripts (window.chrome stubs,
ANGLE WebGL strings, CDP cleanup, HeadlessChrome UA strip) were no-ops or
actively suspicious on Firefox, while Firefox-specific headless vectors
were unaddressed.

Split stealthInitScripts into three categories:
- stealthCommonScripts (4): webdriver, outerWidth/Height, permissions, Notification
- stealthChromiumScripts (8): existing Chromium-specific scripts
- stealthFirefoxScripts (5): new Firefox-specific stealth:
  - navigator.webdriver getOwnPropertyDescriptor hardening
  - WebGL renderer spoof with Mesa/Intel strings
  - mozInnerScreenX/Y non-zero spoof
  - navigator.hardwareConcurrency normalization
  - PDF.js plugin list override

browser_init.go now selects common + engine-specific scripts based on
opt.Browser. Tests updated with per-category validation and cross-
contamination checks.

Closes #69

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

browser_init.go

@@ -61,7 +61,13 @@ func initBrowser(opt BrowserOptions) (*browserInitResult, error) {
 		if opt.Browser == BrowserChromium {
 			launchArgs = append(launchArgs, stealthChromiumArgs...)
 		}
-		initScripts = append(initScripts, stealthInitScripts...)
+		initScripts = append(initScripts, stealthCommonScripts...)
+		switch opt.Browser {
+		case BrowserChromium:
+			initScripts = append(initScripts, stealthChromiumScripts...)
+		case BrowserFirefox:
+			initScripts = append(initScripts, stealthFirefoxScripts...)
+		}
 	}
 
 	launchArgs = append(launchArgs, opt.LaunchArgs...)

stealth.go

@@ -5,81 +5,17 @@ var stealthChromiumArgs = []string{
 	"--disable-blink-features=AutomationControlled",
 }
 
-// stealthInitScripts are JavaScript snippets injected before page scripts to mask automation signals.
+// stealthCommonScripts are JavaScript snippets injected before page scripts on all browser engines.
-var stealthInitScripts = []string{
+var stealthCommonScripts = []string{
 	// Override navigator.webdriver to return undefined (the real-browser value).
 	`Object.defineProperty(navigator, 'webdriver', {get: () => undefined})`,
 
-	// Populate navigator.plugins with a realistic entry so plugins.length > 0.
-	`Object.defineProperty(navigator, 'plugins', {
-		get: () => {
-			const arr = [
-				{ name: 'PDF Viewer', filename: 'internal-pdf-viewer', description: 'Portable Document Format' },
-				{ name: 'Chrome PDF Plugin', filename: 'internal-pdf-viewer', description: '' },
-				{ name: 'Chromium PDF Viewer', filename: 'internal-pdf-viewer', description: '' },
-			];
-			arr.item = (i) => arr[i] || null;
-			arr.namedItem = (n) => arr.find(p => p.name === n) || null;
-			arr.refresh = () => {};
-			return arr;
-		},
-	})`,
-
-	// Populate navigator.mimeTypes to match the fake plugins above.
-	`Object.defineProperty(navigator, 'mimeTypes', {
-		get: () => {
-			const arr = [
-				{ type: 'application/pdf', suffixes: 'pdf', description: 'Portable Document Format' },
-			];
-			arr.item = (i) => arr[i] || null;
-			arr.namedItem = (n) => arr.find(m => m.type === n) || null;
-			return arr;
-		},
-	})`,
-
-	// Provide window.chrome runtime stub (Chromium-only signal; harmless on other engines).
-	`if (!window.chrome) {
-		window.chrome = { runtime: {} };
-	}`,
-
 	// Fix outerWidth/outerHeight which are 0 in headless mode.
 	`if (window.outerWidth === 0) {
 		Object.defineProperty(window, 'outerWidth',  { get: () => window.innerWidth  });
 		Object.defineProperty(window, 'outerHeight', { get: () => window.innerHeight });
 	}`,
 
-	// Spoof WebGL renderer to hide SwiftShader (headless GPU) fingerprint.
-	`(function() {
-		const getParam = WebGLRenderingContext.prototype.getParameter;
-		WebGLRenderingContext.prototype.getParameter = function(param) {
-			if (param === 37445) return 'Google Inc. (Intel)';
-			if (param === 37446) return 'ANGLE (Intel, Intel(R) UHD Graphics 630, OpenGL 4.5)';
-			return getParam.call(this, param);
-		};
-		if (typeof WebGL2RenderingContext !== 'undefined') {
-			const getParam2 = WebGL2RenderingContext.prototype.getParameter;
-			WebGL2RenderingContext.prototype.getParameter = function(param) {
-				if (param === 37445) return 'Google Inc. (Intel)';
-				if (param === 37446) return 'ANGLE (Intel, Intel(R) UHD Graphics 630, OpenGL 4.5)';
-				return getParam2.call(this, param);
-			};
-		}
-	})()`,
-
-	// Add chrome.app, chrome.csi, and chrome.loadTimes stubs missing in headless.
-	`(function() {
-		if (!window.chrome) window.chrome = {};
-		if (!window.chrome.app) {
-			window.chrome.app = { isInstalled: false, InstallState: { DISABLED: 'disabled', INSTALLED: 'installed', NOT_INSTALLED: 'not_installed' }, RunningState: { CANNOT_RUN: 'cannot_run', READY_TO_RUN: 'ready_to_run', RUNNING: 'running' } };
-		}
-		if (!window.chrome.csi) {
-			window.chrome.csi = function() { return { startE: Date.now(), onloadT: Date.now(), pageT: 0, tran: 15 }; };
-		}
-		if (!window.chrome.loadTimes) {
-			window.chrome.loadTimes = function() { return { commitLoadTime: Date.now() / 1000, connectionInfo: 'h2', finishDocumentLoadTime: Date.now() / 1000, finishLoadTime: Date.now() / 1000, firstPaintAfterLoadTime: 0, firstPaintTime: Date.now() / 1000, navigationType: 'Other', npnNegotiatedProtocol: 'h2', requestTime: Date.now() / 1000, startLoadTime: Date.now() / 1000, wasAlternateProtocolAvailable: false, wasFetchedViaSpdy: true, wasNpnNegotiated: true }; };
-		}
-	})()`,
-
 	// Override navigator.permissions.query to return "denied" for notifications.
 	`(function() {
 		if (navigator.permissions && navigator.permissions.query) {
@@ -101,8 +37,75 @@ var stealthInitScripts = []string{
 			Notification.requestPermission = function() { return Promise.resolve('denied'); };
 		}
 	})()`,
+}
 
-	// Stub navigator.connection (Network Information API) if missing.
+// stealthChromiumScripts are JavaScript snippets specific to Chromium-based browsers.
+var stealthChromiumScripts = []string{
+	// Populate navigator.plugins with realistic Chromium entries so plugins.length > 0.
+	`Object.defineProperty(navigator, 'plugins', {
+		get: () => {
+			const arr = [
+				{ name: 'PDF Viewer', filename: 'internal-pdf-viewer', description: 'Portable Document Format' },
+				{ name: 'Chrome PDF Plugin', filename: 'internal-pdf-viewer', description: '' },
+				{ name: 'Chromium PDF Viewer', filename: 'internal-pdf-viewer', description: '' },
+			];
+			arr.item = (i) => arr[i] || null;
+			arr.namedItem = (n) => arr.find(p => p.name === n) || null;
+			arr.refresh = () => {};
+			return arr;
+		},
+	})`,
+
+	// Populate navigator.mimeTypes to match the fake Chromium plugins above.
+	`Object.defineProperty(navigator, 'mimeTypes', {
+		get: () => {
+			const arr = [
+				{ type: 'application/pdf', suffixes: 'pdf', description: 'Portable Document Format' },
+			];
+			arr.item = (i) => arr[i] || null;
+			arr.namedItem = (n) => arr.find(m => m.type === n) || null;
+			return arr;
+		},
+	})`,
+
+	// Provide window.chrome runtime stub (Chromium-only signal).
+	`if (!window.chrome) {
+		window.chrome = { runtime: {} };
+	}`,
+
+	// Add chrome.app, chrome.csi, and chrome.loadTimes stubs missing in headless.
+	`(function() {
+		if (!window.chrome) window.chrome = {};
+		if (!window.chrome.app) {
+			window.chrome.app = { isInstalled: false, InstallState: { DISABLED: 'disabled', INSTALLED: 'installed', NOT_INSTALLED: 'not_installed' }, RunningState: { CANNOT_RUN: 'cannot_run', READY_TO_RUN: 'ready_to_run', RUNNING: 'running' } };
+		}
+		if (!window.chrome.csi) {
+			window.chrome.csi = function() { return { startE: Date.now(), onloadT: Date.now(), pageT: 0, tran: 15 }; };
+		}
+		if (!window.chrome.loadTimes) {
+			window.chrome.loadTimes = function() { return { commitLoadTime: Date.now() / 1000, connectionInfo: 'h2', finishDocumentLoadTime: Date.now() / 1000, finishLoadTime: Date.now() / 1000, firstPaintAfterLoadTime: 0, firstPaintTime: Date.now() / 1000, navigationType: 'Other', npnNegotiatedProtocol: 'h2', requestTime: Date.now() / 1000, startLoadTime: Date.now() / 1000, wasAlternateProtocolAvailable: false, wasFetchedViaSpdy: true, wasNpnNegotiated: true }; };
+		}
+	})()`,
+
+	// Spoof WebGL renderer to hide SwiftShader (headless GPU) fingerprint with Chromium ANGLE strings.
+	`(function() {
+		const getParam = WebGLRenderingContext.prototype.getParameter;
+		WebGLRenderingContext.prototype.getParameter = function(param) {
+			if (param === 37445) return 'Google Inc. (Intel)';
+			if (param === 37446) return 'ANGLE (Intel, Intel(R) UHD Graphics 630, OpenGL 4.5)';
+			return getParam.call(this, param);
+		};
+		if (typeof WebGL2RenderingContext !== 'undefined') {
+			const getParam2 = WebGL2RenderingContext.prototype.getParameter;
+			WebGL2RenderingContext.prototype.getParameter = function(param) {
+				if (param === 37445) return 'Google Inc. (Intel)';
+				if (param === 37446) return 'ANGLE (Intel, Intel(R) UHD Graphics 630, OpenGL 4.5)';
+				return getParam2.call(this, param);
+			};
+		}
+	})()`,
+
+	// Stub navigator.connection (Network Information API) if missing (Chrome-only API).
 	`(function() {
 		if (!navigator.connection) {
 			Object.defineProperty(navigator, 'connection', {
@@ -132,3 +135,66 @@ var stealthInitScripts = []string{
 		}
 	})()`,
 }
+
+// stealthFirefoxScripts are JavaScript snippets specific to Firefox.
+var stealthFirefoxScripts = []string{
+	// Harden navigator.webdriver for Firefox: ensure Object.getOwnPropertyDescriptor also returns undefined.
+	`(function() {
+		const proto = Object.getPrototypeOf(navigator);
+		const origGetOwnPropDesc = Object.getOwnPropertyDescriptor;
+		Object.getOwnPropertyDescriptor = function(obj, prop) {
+			if ((obj === navigator || obj === proto) && prop === 'webdriver') {
+				return undefined;
+			}
+			return origGetOwnPropDesc.call(this, obj, prop);
+		};
+	})()`,
+
+	// Spoof WebGL renderer with Firefox-appropriate Mesa/Intel strings.
+	`(function() {
+		const getParam = WebGLRenderingContext.prototype.getParameter;
+		WebGLRenderingContext.prototype.getParameter = function(param) {
+			if (param === 37445) return 'Intel Open Source Technology Center';
+			if (param === 37446) return 'Mesa DRI Intel(R) UHD Graphics 630';
+			return getParam.call(this, param);
+		};
+		if (typeof WebGL2RenderingContext !== 'undefined') {
+			const getParam2 = WebGL2RenderingContext.prototype.getParameter;
+			WebGL2RenderingContext.prototype.getParameter = function(param) {
+				if (param === 37445) return 'Intel Open Source Technology Center';
+				if (param === 37446) return 'Mesa DRI Intel(R) UHD Graphics 630';
+				return getParam2.call(this, param);
+			};
+		}
+	})()`,
+
+	// Spoof mozInnerScreenX/mozInnerScreenY which are 0 in headless Firefox.
+	`(function() {
+		if (window.mozInnerScreenX === 0) {
+			Object.defineProperty(window, 'mozInnerScreenX', { get: () => 8 });
+		}
+		if (window.mozInnerScreenY === 0) {
+			Object.defineProperty(window, 'mozInnerScreenY', { get: () => 51 });
+		}
+	})()`,
+
+	// Normalize navigator.hardwareConcurrency (Firefox headless sometimes reports 2).
+	`(function() {
+		if (navigator.hardwareConcurrency <= 2) {
+			Object.defineProperty(navigator, 'hardwareConcurrency', { get: () => 4 });
+		}
+	})()`,
+
+	// Override navigator.plugins with Firefox-appropriate PDF.js entry.
+	`Object.defineProperty(navigator, 'plugins', {
+		get: () => {
+			const arr = [
+				{ name: 'PDF.js', filename: 'internal-pdf-viewer', description: 'Portable Document Format' },
+			];
+			arr.item = (i) => arr[i] || null;
+			arr.namedItem = (n) => arr.find(p => p.name === n) || null;
+			arr.refresh = () => {};
+			return arr;
+		},
+	})`,
+}

stealth_test.go

@@ -66,105 +66,311 @@ func TestStealthChromiumArgs(t *testing.T) {
 	}
 }
 
-func TestStealthInitScripts(t *testing.T) {
+// --- Common scripts ---
-	if len(stealthInitScripts) == 0 {
+
-		t.Fatal("expected at least one stealth init script")
+func TestStealthCommonScripts_Count(t *testing.T) {
+	if len(stealthCommonScripts) != 4 {
+		t.Fatalf("expected 4 common stealth scripts, got %d", len(stealthCommonScripts))
 	}
 }
 
-func TestStealthInitScripts_Count(t *testing.T) {
+func TestStealthCommonScripts_WebdriverOverride(t *testing.T) {
-	if len(stealthInitScripts) != 12 {
-		t.Fatalf("expected 12 stealth init scripts, got %d", len(stealthInitScripts))
-	}
-}
-
-func TestStealthInitScripts_WebGLSpoof(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthCommonScripts {
-		if strings.Contains(s, "SwiftShader") || strings.Contains(s, "UNMASKED_RENDERER") || strings.Contains(s, "37446") {
+		if strings.Contains(s, "navigator") && strings.Contains(s, "webdriver") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that spoofs WebGL renderer")
+		t.Fatal("expected a common script that overrides navigator.webdriver")
 	}
 }
 
-func TestStealthInitScripts_ChromeApp(t *testing.T) {
+func TestStealthCommonScripts_OuterDimensions(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthCommonScripts {
-		if strings.Contains(s, "chrome.app") && strings.Contains(s, "chrome.csi") && strings.Contains(s, "chrome.loadTimes") {
+		if strings.Contains(s, "outerWidth") && strings.Contains(s, "outerHeight") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that stubs chrome.app, chrome.csi, and chrome.loadTimes")
+		t.Fatal("expected a common script that fixes outerWidth/outerHeight")
 	}
 }
 
-func TestStealthInitScripts_PermissionsQuery(t *testing.T) {
+func TestStealthCommonScripts_PermissionsQuery(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthCommonScripts {
 		if strings.Contains(s, "permissions.query") && strings.Contains(s, "notifications") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that overrides permissions.query for notifications")
+		t.Fatal("expected a common script that overrides permissions.query for notifications")
 	}
 }
 
-func TestStealthInitScripts_Notification(t *testing.T) {
+func TestStealthCommonScripts_Notification(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthCommonScripts {
 		if strings.Contains(s, "Notification") && strings.Contains(s, "requestPermission") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that stubs Notification constructor")
+		t.Fatal("expected a common script that stubs Notification constructor")
 	}
 }
 
-func TestStealthInitScripts_NavigatorConnection(t *testing.T) {
+// --- Chromium scripts ---
+
+func TestStealthChromiumScripts_Count(t *testing.T) {
+	if len(stealthChromiumScripts) != 8 {
+		t.Fatalf("expected 8 chromium stealth scripts, got %d", len(stealthChromiumScripts))
+	}
+}
+
+func TestStealthChromiumScripts_Plugins(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthChromiumScripts {
+		if strings.Contains(s, "Chrome PDF Plugin") && strings.Contains(s, "navigator") && strings.Contains(s, "plugins") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a chromium script that populates navigator.plugins with Chrome entries")
+	}
+}
+
+func TestStealthChromiumScripts_MimeTypes(t *testing.T) {
+	found := false
+	for _, s := range stealthChromiumScripts {
+		if strings.Contains(s, "mimeTypes") && strings.Contains(s, "application/pdf") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a chromium script that populates navigator.mimeTypes")
+	}
+}
+
+func TestStealthChromiumScripts_WindowChrome(t *testing.T) {
+	found := false
+	for _, s := range stealthChromiumScripts {
+		if strings.Contains(s, "window.chrome") && strings.Contains(s, "runtime") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a chromium script that stubs window.chrome")
+	}
+}
+
+func TestStealthChromiumScripts_ChromeApp(t *testing.T) {
+	found := false
+	for _, s := range stealthChromiumScripts {
+		if strings.Contains(s, "chrome.app") && strings.Contains(s, "chrome.csi") && strings.Contains(s, "chrome.loadTimes") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a chromium script that stubs chrome.app, chrome.csi, and chrome.loadTimes")
+	}
+}
+
+func TestStealthChromiumScripts_WebGLSpoof(t *testing.T) {
+	found := false
+	for _, s := range stealthChromiumScripts {
+		if strings.Contains(s, "37446") && strings.Contains(s, "ANGLE") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a chromium script that spoofs WebGL renderer with ANGLE strings")
+	}
+}
+
+func TestStealthChromiumScripts_NavigatorConnection(t *testing.T) {
+	found := false
+	for _, s := range stealthChromiumScripts {
 		if strings.Contains(s, "connection") && strings.Contains(s, "effectiveType") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that stubs navigator.connection")
+		t.Fatal("expected a chromium script that stubs navigator.connection")
 	}
 }
 
-func TestStealthInitScripts_CDPCleanup(t *testing.T) {
+func TestStealthChromiumScripts_CDPCleanup(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthChromiumScripts {
 		if strings.Contains(s, "cdc_") && strings.Contains(s, "delete") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that cleans up CDP artifacts")
+		t.Fatal("expected a chromium script that cleans up CDP artifacts")
 	}
 }
 
-func TestStealthInitScripts_UserAgentStrip(t *testing.T) {
+func TestStealthChromiumScripts_UserAgentStrip(t *testing.T) {
 	found := false
-	for _, s := range stealthInitScripts {
+	for _, s := range stealthChromiumScripts {
 		if strings.Contains(s, "HeadlessChrome") && strings.Contains(s, "userAgent") {
 			found = true
 			break
 		}
 	}
 	if !found {
-		t.Fatal("expected a stealth script that strips HeadlessChrome from user agent")
+		t.Fatal("expected a chromium script that strips HeadlessChrome from user agent")
+	}
+}
+
+// --- Firefox scripts ---
+
+func TestStealthFirefoxScripts_Count(t *testing.T) {
+	if len(stealthFirefoxScripts) != 5 {
+		t.Fatalf("expected 5 firefox stealth scripts, got %d", len(stealthFirefoxScripts))
+	}
+}
+
+func TestStealthFirefoxScripts_WebdriverHardening(t *testing.T) {
+	found := false
+	for _, s := range stealthFirefoxScripts {
+		if strings.Contains(s, "getOwnPropertyDescriptor") && strings.Contains(s, "webdriver") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a firefox script that hardens navigator.webdriver via getOwnPropertyDescriptor")
+	}
+}
+
+func TestStealthFirefoxScripts_WebGLSpoof(t *testing.T) {
+	found := false
+	for _, s := range stealthFirefoxScripts {
+		if strings.Contains(s, "37446") && strings.Contains(s, "Mesa DRI") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a firefox script that spoofs WebGL renderer with Mesa strings")
+	}
+}
+
+func TestStealthFirefoxScripts_MozInnerScreen(t *testing.T) {
+	found := false
+	for _, s := range stealthFirefoxScripts {
+		if strings.Contains(s, "mozInnerScreenX") && strings.Contains(s, "mozInnerScreenY") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a firefox script that spoofs mozInnerScreenX/mozInnerScreenY")
+	}
+}
+
+func TestStealthFirefoxScripts_HardwareConcurrency(t *testing.T) {
+	found := false
+	for _, s := range stealthFirefoxScripts {
+		if strings.Contains(s, "hardwareConcurrency") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a firefox script that normalizes navigator.hardwareConcurrency")
+	}
+}
+
+func TestStealthFirefoxScripts_PDFjsPlugins(t *testing.T) {
+	found := false
+	for _, s := range stealthFirefoxScripts {
+		if strings.Contains(s, "PDF.js") && strings.Contains(s, "plugins") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("expected a firefox script that provides PDF.js plugin entry")
+	}
+}
+
+// --- Cross-category validation ---
+
+func TestStealthScripts_NoOverlap(t *testing.T) {
+	all := make(map[string]string) // script -> category
+	for _, s := range stealthCommonScripts {
+		all[s] = "common"
+	}
+	for _, s := range stealthChromiumScripts {
+		if cat, ok := all[s]; ok {
+			t.Fatalf("chromium script also appears in %s category", cat)
+		}
+		all[s] = "chromium"
+	}
+	for _, s := range stealthFirefoxScripts {
+		if cat, ok := all[s]; ok {
+			t.Fatalf("firefox script also appears in %s category", cat)
+		}
+	}
+}
+
+func TestStealthCommonScripts_NoChromiumMarkers(t *testing.T) {
+	chromiumMarkers := []string{"window.chrome", "chrome.app", "chrome.csi", "chrome.loadTimes", "HeadlessChrome", "cdc_", "Chrome PDF Plugin", "ANGLE"}
+	for _, s := range stealthCommonScripts {
+		for _, marker := range chromiumMarkers {
+			if strings.Contains(s, marker) {
+				t.Fatalf("common script contains Chromium-specific marker %q", marker)
+			}
+		}
+	}
+}
+
+func TestStealthCommonScripts_NoFirefoxMarkers(t *testing.T) {
+	firefoxMarkers := []string{"mozInnerScreen", "Mesa DRI", "PDF.js"}
+	for _, s := range stealthCommonScripts {
+		for _, marker := range firefoxMarkers {
+			if strings.Contains(s, marker) {
+				t.Fatalf("common script contains Firefox-specific marker %q", marker)
+			}
+		}
+	}
+}
+
+func TestStealthChromiumScripts_NoFirefoxMarkers(t *testing.T) {
+	firefoxMarkers := []string{"mozInnerScreen", "Mesa DRI", "PDF.js"}
+	for _, s := range stealthChromiumScripts {
+		for _, marker := range firefoxMarkers {
+			if strings.Contains(s, marker) {
+				t.Fatalf("chromium script contains Firefox-specific marker %q", marker)
+			}
+		}
+	}
+}
+
+func TestStealthFirefoxScripts_NoChromiumMarkers(t *testing.T) {
+	chromiumMarkers := []string{"window.chrome", "chrome.app", "chrome.csi", "chrome.loadTimes", "HeadlessChrome", "cdc_", "Chrome PDF Plugin", "ANGLE"}
+	for _, s := range stealthFirefoxScripts {
+		for _, marker := range chromiumMarkers {
+			if strings.Contains(s, marker) {
+				t.Fatalf("firefox script contains Chromium-specific marker %q", marker)
+			}
+		}
 	}
 }