fix referrer encoding

Author: dnywh

src/app/actions.ts

@@ -13,6 +13,24 @@ import { headers } from "next/headers";
 import { redirect } from "next/navigation";
 import { getTranslations } from "next-intl/server";
 
+const normaliseReferrer = (referrer: string | undefined) => {
+  if (!referrer) return undefined;
+
+  let current = referrer;
+
+  for (let i = 0; i < 3; i += 1) {
+    try {
+      const decoded = decodeURIComponent(current);
+      if (decoded === current) break;
+      current = decoded;
+    } catch {
+      break;
+    }
+  }
+
+  return current;
+};
+
 export const signUpAction = async (formData: FormData, request?: Request) => {
   const t = await getTranslations("Errors");
   const email = formData.get("email")?.toString();
@@ -28,7 +46,9 @@ export const signUpAction = async (formData: FormData, request?: Request) => {
   const origin = headersList.get("origin");
 
   // Get attribution data
-  const referrer = formData.get("initial_referrer")?.toString();
+  const referrer = normaliseReferrer(
+    formData.get("initial_referrer")?.toString()
+  );
   const utmSource = formData.get("utm_source")?.toString();
   const utmMedium = formData.get("utm_medium")?.toString();
   const utmCampaign = formData.get("utm_campaign")?.toString();

src/proxy.ts

@@ -36,17 +36,13 @@ export async function proxy(request: NextRequest) {
     externalReferrer &&
     request.method === "GET"
   ) {
-    response.cookies.set(
-      INITIAL_REFERRER_COOKIE,
-      encodeURIComponent(externalReferrer),
-      {
-        httpOnly: false,
-        maxAge: INITIAL_REFERRER_MAX_AGE,
-        path: "/",
-        sameSite: "lax",
-        secure: request.nextUrl.protocol === "https:",
-      }
-    );
+    response.cookies.set(INITIAL_REFERRER_COOKIE, externalReferrer, {
+      httpOnly: false,
+      maxAge: INITIAL_REFERRER_MAX_AGE,
+      path: "/",
+      sameSite: "lax",
+      secure: request.nextUrl.protocol === "https:",
+    });
   }
 
   return response;

src/utils/attributionUtils.ts

@@ -47,12 +47,28 @@ const getCookie = (name: string): string | null => {
   if (!value) return null;
 
   try {
-    return decodeURIComponent(value);
+    return normaliseReferrer(value);
   } catch {
     return value;
   }
 };
 
+const normaliseReferrer = (referrer: string): string => {
+  let current = referrer;
+
+  for (let i = 0; i < 3; i += 1) {
+    try {
+      const decoded = decodeURIComponent(current);
+      if (decoded === current) break;
+      current = decoded;
+    } catch {
+      break;
+    }
+  }
+
+  return current;
+};
+
 const getExternalDocumentReferrer = (): string | null => {
   const referrer = document.referrer;
 
@@ -72,7 +88,7 @@ const getExternalDocumentReferrer = (): string | null => {
 };
 
 const storeInitialReferrer = (referrer: string) => {
-  localStorage.setItem(INITIAL_REFERRER_KEY, referrer);
+  localStorage.setItem(INITIAL_REFERRER_KEY, normaliseReferrer(referrer));
 };
 
 export function captureAttributionParams() {
@@ -125,10 +141,17 @@ export function getStoredAttributionParams(): StoredAttributionParams {
     const stored = localStorage.getItem(UTM_STORAGE_KEY);
     const storedInitialReferrer = localStorage.getItem(INITIAL_REFERRER_KEY);
     const cookieReferrer = getCookie(INITIAL_REFERRER_COOKIE);
-    const initialReferrer = storedInitialReferrer ?? cookieReferrer;
+    const initialReferrer = storedInitialReferrer
+      ? normaliseReferrer(storedInitialReferrer)
+      : cookieReferrer;
 
     if (!storedInitialReferrer && initialReferrer) {
       storeInitialReferrer(initialReferrer);
+    } else if (
+      storedInitialReferrer &&
+      initialReferrer !== storedInitialReferrer
+    ) {
+      storeInitialReferrer(initialReferrer);
     }
 
     return {