Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-84139

CVE-2026-84139MEDIUM

Mozilla Firefox — Clickjacking issue in the DOM: Events component

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   R  C  L  L  N    6.1   .0034   24.9     —

AFFECTED
  Product      Versions     Fixed
  Firefox      unspecified  153.2
  Thunderbird  unspecified  153.2

TIMELINE
  Sep 1   Reserved by mozilla
  Sep 1   Published (CNA: mozilla)
  Sep 3   RESCORED — CVE-2026-84139 (Mozilla Firefox). CVSS 9.8 → 6.1 (NVD).

CWE-1021 · CNA: mozilla · CVSS v3.1 · 5 references · NVD status: Modified

Description

Clickjacking issue in the DOM: Events component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
September 1, 2026	Reserved	Reserved by mozilla
September 1, 2026	Published	Published (CNA: mozilla)
September 3, 2026	RESCORED	RESCORED — CVE-2026-84139 (Mozilla Firefox). CVSS 9.8 → 6.1 (NVD).

Affected

Affected products and packages — 2 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Mozilla	Firefox	—	—	153.2
Mozilla	Thunderbird	—	—	153.2

Weaknesses

CWE-1021

References (5)

https://bugzilla.mozilla.org/show_bug.cgi?id=2060153 [Issue Tracking, Permissions Required]
https://www.mozilla.org/security/advisories/mfsa2026-82/ [Vendor Advisory]
https://www.mozilla.org/security/advisories/mfsa2026-85/ [Vendor Advisory]
https://www.mozilla.org/security/advisories/mfsa2026-86/ [Vendor Advisory]
https://www.mozilla.org/security/advisories/mfsa2026-88/ [Vendor Advisory]

Authoritative record: CVE-2026-84139 at cve.org

Vendors: mozilla

Weaknesses: CWE-1021

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-84139 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.