--- title: "CVE-2026-100828: Firefox ESR - Mitigation Bypass" description: "Firefox ESR contains a mitigation bypass vulnerability in the Bookmarks & History component, letting attackers bypass security mitigations, exploit requires unspecified conditions." url: https://panop.io/threat-heartbeat/CVE-2026-100828/ --- # CVE-2026-100828 Firefox ESR - Mitigation Bypass Firefox ESR contains a mitigation bypass vulnerability in the Bookmarks & History component, letting attackers bypass security mitigations, exploit requires unspecified conditions. CVSS base score 9.6 /10 Critical CISA KEV Not listed Public exploit None known EPSS 0.24% chance of exploitation in 30 days [View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-100828) ## Details Type Mitigation Bypass CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H Published 29 September 2026 Updated 15 October 2026 Weakness [CWE-693](https://cwe.mitre.org/data/definitions/693.html) ## Vendor fix Update to Firefox ESR 153.4, 157 or later. Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them. ## References - [https://nvd.nist.gov/vuln/detail/CVE-2026-100828](https://nvd.nist.gov/vuln/detail/CVE-2026-100828) - [https://bugzilla.mozilla.org/show\_bug.cgi?id=2066019](https://bugzilla.mozilla.org/show_bug.cgi?id=2066019) - [https://www.mozilla.org/security/advisories/mfsa2026-100/](https://www.mozilla.org/security/advisories/mfsa2026-100/) - [https://www.mozilla.org/security/advisories/mfsa2026-97/](https://www.mozilla.org/security/advisories/mfsa2026-97/) - [https://www.mozilla.org/security/advisories/mfsa2026-101/](https://www.mozilla.org/security/advisories/mfsa2026-101/) - [https://www.mozilla.org/security/advisories/mfsa2026-103/](https://www.mozilla.org/security/advisories/mfsa2026-103/) [← All CVEs](https://panop.io/threat-heartbeat/) ## What this record can't tell you - Whether you run the affected software, and where - Whether an attacker can actually reach and exploit it - The misconfigurations that never get a CVE number - What it would cost the business, ranked into what to fix first Panop answers these inside your environment, for this CVE and every other finding. [Book a demo](https://panop.io/demo)