Sean Oliver 075c2f4528 fix(common): resolve double-encoding in first-referrer cookie serialization (#43617)
## Problem

While working on the phased PostHog Attribution rollout (GROWTH-625 /
GROWTH-668) — specifically the initial referrer handoff across the app
boundary — we discovered that `parseFirstReferrerCookie` was returning
`null` even when the cookie was visibly present in the browser.

The root cause: `serializeFirstReferrerCookie` calls
`encodeURIComponent(JSON.stringify(data))`, but Next.js `cookies.set()`
encodes the value again, producing a double-encoded cookie. On the read
side, `parseFirstReferrerCookie` only decodes once, so `JSON.parse`
receives a still-encoded string and fails. The `try/catch` swallows the
error and returns `null`.

Confirmed in production: the raw cookie value starts with `%257B%2522`
(double-encoded `%` characters). A single `decodeURIComponent` produces
`%7B%22referrer%22...` — still URL-encoded, not valid JSON. This was
blocking the cross-app attribution handoff that GROWTH-625 depends on.

## Changes

- **Serializer**: Removed `encodeURIComponent` from
`serializeFirstReferrerCookie` — Next.js `cookies.set()` already handles
encoding
- **Parser**: Made `parseFirstReferrerCookie` resilient to both
encodings — tries single decode first, falls back to double decode for
existing cookies in the wild (365-day TTL means legacy cookies persist
up to a year)
- **Test**: Added unit test for the double-encoded legacy cookie format

## Testing

- 35/35 common unit tests pass, 12/12 www middleware tests pass
- Verified locally: Google → www (localhost:3000) → Studio
(localhost:8082). Console logs confirmed `parseFirstReferrerCookie`
returned the full data object instead of null
- Confirmed in production that existing cookies are double-encoded and
the fix correctly handles them

Ref: GROWTH-625 / GROWTH-668
2026-03-11 13:08:11 -07:00
2026-02-11 09:50:11 +01:00
2026-03-11 18:40:01 +00:00
2026-03-11 18:40:01 +00:00
2025-06-17 11:08:46 +02:00
2024-01-10 13:34:41 +01:00
2021-07-25 12:45:26 +08:00
2023-03-11 19:47:56 +01:00

Supabase

Supabase is the Postgres development platform. We're building the features of Firebase using enterprise-grade open source tools.

  • Hosted Postgres Database. Docs
  • Authentication and Authorization. Docs
  • Auto-generated APIs.
  • Functions.
    • Database Functions. Docs
    • Edge Functions Docs
  • File Storage. Docs
  • AI + Vector/Embeddings Toolkit. Docs
  • Dashboard

Supabase Dashboard

Watch "releases" of this repo to get notified of major updates.

Watch this repo

Documentation

For full documentation, visit supabase.com/docs

To see how to Contribute, visit Getting Started

Community & Support

  • Community Forum. Best for: help with building, discussion about database best practices.
  • GitHub Issues. Best for: bugs and errors you encounter using Supabase.
  • Email Support. Best for: problems with your database or infrastructure.
  • Discord. Best for: sharing your applications and hanging out with the community.

How it works

Supabase is a combination of open source tools. We’re building the features of Firebase using enterprise-grade, open source products. If the tools and communities exist, with an MIT, Apache 2, or equivalent open license, we will use and support that tool. If the tool doesn't exist, we build and open source it ourselves. Supabase is not a 1-to-1 mapping of Firebase. Our aim is to give developers a Firebase-like developer experience using open source tools.

Architecture

Supabase is a hosted platform. You can sign up and start using Supabase without installing anything. You can also self-host and develop locally.

Architecture

  • Postgres is an object-relational database system with over 30 years of active development that has earned it a strong reputation for reliability, feature robustness, and performance.
  • Realtime is an Elixir server that allows you to listen to PostgreSQL inserts, updates, and deletes using websockets. Realtime polls Postgres' built-in replication functionality for database changes, converts changes to JSON, then broadcasts the JSON over websockets to authorized clients.
  • PostgREST is a web server that turns your PostgreSQL database directly into a RESTful API.
  • GoTrue is a JWT-based authentication API that simplifies user sign-ups, logins, and session management in your applications.
  • Storage a RESTful API for managing files in S3, with Postgres handling permissions.
  • pg_graphql a PostgreSQL extension that exposes a GraphQL API.
  • postgres-meta is a RESTful API for managing your Postgres, allowing you to fetch tables, add roles, and run queries, etc.
  • Kong is a cloud-native API gateway.

Client libraries

Our approach for client libraries is modular. Each sub-library is a standalone implementation for a single external system. This is one of the ways we support existing tools.

Language Client Feature-Clients (bundled in Supabase client)
Supabase PostgREST GoTrue Realtime Storage Functions
⚡️ Official ⚡️
JavaScript (TypeScript) supabase-js postgrest-js auth-js realtime-js storage-js functions-js
Flutter supabase-flutter postgrest-dart gotrue-dart realtime-dart storage-dart functions-dart
Swift supabase-swift postgrest-swift auth-swift realtime-swift storage-swift functions-swift
Python supabase-py postgrest-py gotrue-py realtime-py storage-py functions-py
💚 Community 💚
C# supabase-csharp postgrest-csharp gotrue-csharp realtime-csharp storage-csharp functions-csharp
Go - postgrest-go gotrue-go - storage-go functions-go
Java - - gotrue-java - storage-java -
Kotlin supabase-kt postgrest-kt auth-kt realtime-kt storage-kt functions-kt
Ruby supabase-rb postgrest-rb - - - -
Rust - postgrest-rs - - - -
Godot Engine (GDScript) supabase-gdscript - - - - -

Badges

Made with Supabase

[![Made with Supabase](https://supabase.com/badge-made-with-supabase.svg)](https://supabase.com)
<a href="https://supabase.com">
  <img
    width="168"
    height="30"
    src="https://supabase.com/badge-made-with-supabase.svg"
    alt="Made with Supabase"
  />
</a>

Made with Supabase (dark)

[![Made with Supabase](https://supabase.com/badge-made-with-supabase-dark.svg)](https://supabase.com)
<a href="https://supabase.com">
  <img
    width="168"
    height="30"
    src="https://supabase.com/badge-made-with-supabase-dark.svg"
    alt="Made with Supabase"
  />
</a>

Translations

Languages
TypeScript 59.3%
MDX 21.5%
JavaScript 17.9%
CSS 0.6%
Shell 0.4%
Other 0.2%