---
id: CVE-2026-8964
title: Spoofing issue in the Popup Blocker component
summary: >-
  Spoofing issue in the Popup Blocker component. This vulnerability was fixed in
  Firefox 151 and Thunderbird 151.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-451
vendor: mozilla
product: firefox
affected:
  - firefox < 151.0.0
  - thunderbird < 151.0.0
patched:
  - firefox 151.0.0
  - thunderbird 151.0.0
published: '2026-05-19'
updated: '2026-07-23'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-8964'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=2025170'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-46/'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2026-50/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00302
epssPercentile: 0.23168
ingestedAt: '2026-07-23T20:19:19.063Z'
---

## Overview

Spoofing issue in the Popup Blocker component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

## Affected

- `firefox < 151.0.0`
- `thunderbird < 151.0.0`

## Remediation

Upgrade past the affected range:

- `firefox 151.0.0`
- `thunderbird 151.0.0`