fix: skip generated config properties the installed Camoufox dropped

src/utils.ts

@@ -676,8 +676,20 @@ export async function launchOptions({
 		}
 	}
 
-	// Inject the fingerprint into the config
-	mergeInto(config, fromBrowserforge(fingerprint, ff_version_str));
+	// Load the installed build's property schema up front: BrowserForge's
+	// mapping and the hardcoded additions below can target properties a newer
+	// Camoufox has dropped (v156 removed navigator.product/appCodeName/appName,
+	// battery:*, screen.pageXOffset/pageYOffset, window.history.length and
+	// canvas:aaOffset/aaCapOffset). Filter what WE generate so validateConfig
+	// only ever throws on caller-supplied mistakes, never on our own output.
+	const knownProperties = loadProperties(executable_path);
+	const fingerprintConfig = fromBrowserforge(fingerprint, ff_version_str);
+	for (const key of Object.keys(fingerprintConfig)) {
+		if (!(key in knownProperties)) {
+			delete fingerprintConfig[key];
+		}
+	}
+	mergeInto(config, fingerprintConfig);
 
 	// Add seeds (BrowserForge doesn't generate these). Mirrors fingerprints.py,
 	// which seeds these right after from_browserforge() with setdefault. Range is
@@ -690,7 +702,6 @@ export async function launchOptions({
 	// builds, so seed only what the installed browser's schema knows.
 	const randint = (min: number, max: number) =>
 		Math.floor(Math.random() * (max - min + 1)) + min;
-	const knownProperties = loadProperties(executable_path);
 	for (const seed of ["fonts:spacing_seed", "audio:seed", "canvas:seed"]) {
 		if (seed in knownProperties) {
 			setInto(config, seed, randint(1, 4_294_967_295));
@@ -699,8 +710,11 @@ export async function launchOptions({
 
 	const targetOS = getTargetOS(config);
 
-	// Set a random window.history.length
-	setInto(config, "window.history.length", Math.floor(Math.random() * 5) + 1);
+	// Set a random window.history.length (only when the installed build knows
+	// it — removed in Camoufox v156)
+	if ("window.history.length" in knownProperties) {
+		setInto(config, "window.history.length", Math.floor(Math.random() * 5) + 1);
+	}
 
 	// Update fonts list
 	if (fonts) {
@@ -813,11 +827,17 @@ export async function launchOptions({
 		});
 	}
 
-	// Canvas anti-fingerprinting
-	mergeInto(config, {
+	// Canvas anti-fingerprinting (only properties the installed build knows —
+	// canvas:* was dropped in Camoufox v156)
+	const canvasAntiFingerprinting: Record<string, number | boolean> = {
 		"canvas:aaOffset": Math.floor(Math.random() * 101) - 50, // nosec
 		"canvas:aaCapOffset": true,
-	});
+	};
+	for (const [key, value] of Object.entries(canvasAntiFingerprinting)) {
+		if (key in knownProperties) {
+			config[key] = value;
+		}
+	}
 
 	// Cache previous pages, requests, etc (uses more memory)
 	if (enable_cache) {

test/utils.test.ts

@@ -112,3 +112,66 @@ describe("launchOptions seeding", () => {
 		).rejects.toThrow("Unknown property audio:seed in config");
 	});
 });
+
+describe("launchOptions dropped-property filtering", () => {
+	const readConfig = (env: Record<string, unknown>) =>
+		JSON.parse(
+			Object.keys(env)
+				.filter((k) => k.startsWith("CAMOU_CONFIG_"))
+				.sort()
+				.map((k) => env[k])
+				.join(""),
+		);
+
+	// Simulates a newer browser whose properties.json no longer declares the
+	// properties BrowserForge/hardcoded additions target (Camoufox v156 dropped
+	// navigator.product/appCodeName/appName, battery:*, screen.pageXOffset,
+	// window.history.length and canvas:aaOffset/aaCapOffset).
+	const DROPPED = [
+		"navigator.product",
+		"navigator.appCodeName",
+		"navigator.appName",
+		"battery:charging",
+		"battery:chargingTime",
+		"battery:dischargingTime",
+		"screen.pageXOffset",
+		"screen.pageYOffset",
+		"window.history.length",
+		"canvas:aaOffset",
+		"canvas:aaCapOffset",
+	];
+	const newerBrowserDir = () => {
+		const dir = fs.mkdtempSync(path.join(os.tmpdir(), "camoufox-newer-"));
+		const properties = JSON.parse(
+			fs.readFileSync(getPath("properties.json"), "utf-8"),
+		).filter(
+			(p: { property: string }) => !DROPPED.includes(p.property),
+		);
+		fs.writeFileSync(
+			path.join(dir, "properties.json"),
+			JSON.stringify(properties),
+		);
+		return path.join(dir, "camoufox-bin");
+	};
+
+	test("generated config omits properties the installed browser dropped", async () => {
+		const { env } = await launchOptions({
+			headless: true,
+			executable_path: newerBrowserDir(),
+		});
+		const config = readConfig(env);
+		for (const key of DROPPED) {
+			expect(config).not.toHaveProperty(key);
+		}
+	});
+
+	test("still rejects an explicitly passed dropped property", async () => {
+		await expect(
+			launchOptions({
+				headless: true,
+				executable_path: newerBrowserDir(),
+				config: { "navigator.product": "Gecko" },
+			}),
+		).rejects.toThrow("Unknown property navigator.product in config");
+	});
+});