---
id: CVE-2026-85268
title: Cross-Site Scripting (XSS) in Firebase Auth Handler via Malicious Bundle ID
summary: >-
  A Cross-Site Scripting (XSS) (CWE-79) vulnerability in the auth/handler in
  Google Cloud Identity Platform and Firebase Authentication versions prior to
  2026-08-14 on iOS allows an unauthenticated remote attacker to execute
  arbitrary Java…
severity: high
cvss: 8.7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/U:Amber'
cvssSource: cna
cwe:
  - CWE-79
vendor: Google Cloud
product: Identity Platform and Firebase Authentication
affected:
  - identity_platform_and_firebase_authentication < 2026-08-14
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-30T16:48:10.216800Z'
published: '2026-10-30'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T16:48:22.519Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-85268'
references:
  - url: 'https://firebase.google.com/support/releases#auth-helper-fix'
tags:
  - cve.org
epss: 0.00581
epssPercentile: 0.47851
ingestedAt: '2026-11-05T16:24:31.089Z'
---

## Overview

A Cross-Site Scripting (XSS) (CWE-79) vulnerability in the auth/handler in Google Cloud Identity Platform and Firebase Authentication versions prior to 2026-08-14 on iOS allows an unauthenticated remote attacker to execute arbitrary JavaScript using a malicious iOS bundle ID.

## Affected

- `identity_platform_and_firebase_authentication < 2026-08-14`

## Remediation

This vulnerability has been patched for all users and no app updates are required. Action is only needed for developers who followed Option 4 (self-hosting the helper code) in the Firebase redirect best practices documentation https://firebase.google.com/docs/auth/web/redirect-best-practices#self-host-helper-code. These users should re-synchronize the helper code to make sure they are hosting the latest version.