---
id: CVE-2024-9398
title: >-
  By checking the result of calls to `window.open` with specifically set
  protocol handlers, an attacker could determine if the application which
  implements that protocol handler is installed
summary: >-
  By checking the result of calls to `window.open` with specifically set
  protocol handlers, an attacker could determine if the application which
  implements that protocol handler is installed. This vulnerability affects
  Firefox < 131, Firef…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-203
vendor: mozilla
product: firefox
affected:
  - firefox < 128.3.0
  - firefox < 131.0
  - thunderbird < 128.3
  - thunderbird = 129.0
patched:
  - firefox 131.0
  - thunderbird 128.3
published: '2024-10-01'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T15:37:15.650'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2024-9398'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1881037'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2024-46/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2024-47/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2024-49/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2024-50/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00566
epssPercentile: 0.45192
ingestedAt: '2026-10-08T15:49:37.971Z'
---

## Overview

By checking the result of calls to `window.open` with specifically set protocol handlers, an attacker could determine if the application which implements that protocol handler is installed. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Thunderbird < 128.3, and Thunderbird < 131.

## Affected

- `firefox < 128.3.0`
- `firefox < 131.0`
- `thunderbird < 128.3`
- `thunderbird = 129.0`

## Remediation

Upgrade past the affected range:

- `firefox 131.0`
- `thunderbird 128.3`