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Full vulnerability report · 2026
CVE-2026-84139High confidence

Clickjacking issue in the DOM: Events component

Mozilla · Firefox

6.1MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.34% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Mozilla Firefox and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

3 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian sidsid · sourcefirefoxVendor fix publishedDebian records a fixed source-package version for this release.155.0-1Debian Security Tracker ↗Source updated 6 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivemozjs102Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivemozjs115Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

2 current
CVE-2026-84139 · CSAF 2.0 · revision 11 · interimSUSE Product Security TeamCVE-2026-84139
80 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • MozillaFirefox as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • MozillaFirefox-devel as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • MozillaFirefox-translations-common as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • MozillaFirefox as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • MozillaFirefox-devel as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • MozillaFirefox-translations-common as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • MozillaFirefox-translations-other as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • MozillaFirefox as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • MozillaFirefox-devel as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • MozillaFirefox-translations-common as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • MozillaFirefox-translations-other as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • MozillaFirefox as component of SUSE Linux Enterprise High Performance Computing 15 SP3
Summary
Clickjacking issue in the DOM: Events component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Remediation
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
CVE-2026-84139 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityfirefox: thunderbird: Clickjacking issue in the DOM: Events component
23 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • firefox as a component of Red Hat Enterprise Linux 10
  • firefox.src as a component of Red Hat Enterprise Linux 10
  • rhel10/firefox-flatpak as a component of Red Hat Enterprise Linux 10
  • rhel10/thunderbird-flatpak as a component of Red Hat Enterprise Linux 10
  • thunderbird as a component of Red Hat Enterprise Linux 10
  • thunderbird.src as a component of Red Hat Enterprise Linux 10
  • firefox as a component of Red Hat Enterprise Linux 6
  • firefox.src as a component of Red Hat Enterprise Linux 6
  • thunderbird as a component of Red Hat Enterprise Linux 6
  • thunderbird.src as a component of Red Hat Enterprise Linux 6
  • firefox as a component of Red Hat Enterprise Linux 7
  • firefox.src as a component of Red Hat Enterprise Linux 7
Summary
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Clickjacking issue in the DOM: Events component
Remediation
No remediation text is recorded.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-69087

No EUVD known-exploited evidence

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

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
9.8 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

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

What

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

Why

The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain.

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

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

Why

The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain.

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Improper Restriction of Rendered UI Layers or Frames → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-1021 ↗

CWE-1021: Improper Restriction of Rendered UI Layers or Frames. The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SChangedScope: The attack can affect a component governed by a different security authority.CLowConfidentiality impact: A successful attack can cause a limited loss.ILowIntegrity impact: A successful attack can cause a limited loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-1021
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-69087Official EUVD mapping

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

Official EUVD record ↗
BSI · German · WID-SEC-2026-3132Mozilla Firefox und Thunderbird: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Mozilla Firefox und Thunderbird ausnutzen, um Berechtigungen zu erweitern, Sicherheitsmaßnahmen zu umgehen, sensible Informationen offenzulegen, Daten zu manipulieren, Spoofing-Angriffe durchzuführen, möglicherweise durch Speicherbeschädigungen beliebigen Code auszuführen oder Denial-of-Service-Zustände herbeizuführen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1106Multiples vulnérabilités dans les produits Mozilla

d?id=CVE-2026-84130 Référence CVE CVE-2026-84131 https://www.cve.org/CVERecord?id=CVE-2026-84131 Référence CVE CVE-2026-84132 https://www.cve.org/CVERecord?id=CVE-2026-84132 Référence CVE CVE-2026-84133 https://www.cve.org/CVERecord?id=CVE-2026-84133 Référence CVE CVE-2026-84134 https://www.cve.org/CVERecord?id=CVE-2026-84134 Référence CVE CVE-2026-84135 https://www.cve.org/CVERecord?id=CVE-2026-84135 Référence CVE CVE-2026-84136 https://www.cve.org/CVERecord?id=CVE-2026-84136 Référence CVE CVE-2026-84137 https://www.cve.org/CVERecord?id=CVE-2026-84137 Référence CVE CVE-2026-84138 https://www.cve.org/CVERecord?id=CVE-2026-84138 Référence CVE CVE-2026-84139 https://www.cve.org/CVERecord?id=CVE-2026-84139 Référence CVE CVE-2026-84140 https://www.cve.org/CVERecord?id=CVE-2026-84140 Référence CVE CVE-2026-84141 https://www.cve.org/CVERecord?id=CVE-2026-84141 Référence CVE CVE-2026-84142 https://www.cve.org/CVERecord?id=CVE-2026-84142 Référence CVE CVE-2026-84143 https://www.cve.org/CVERecord?id=CVE-2026-84143 Référence CVE CVE-2026-84144 https://www.cve.org/CVERecord?id=CVE-2026-84144 Référence CVE CVE-2026-84145 https://www.cve.org/CVERecord?id=CVE-2026-84145 Référence CVE CVE-2026-84637 https://www.cve.org/CVERecord?id=CVE-2026-84637 Référence CVE CVE-2026-84639 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-031892Mozilla FoundationのMozilla Firefox等の複数製品におけるレンダリングされたユーザインターフェースレイヤまたはフレームの不適切な制限に関する脆弱性

DOMのEventsコンポーネントに存在するクリックジャッキングの問題です。この脆弱性はFirefox 155、Firefox ESR 153.2、Thunderbird 155、およびThunderbird 153.2で修正されました。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
Action
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles8 stored documents

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

  • Security Vulnerabilities fixed in Firefox 155 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Firefox 155 Announced September 1, 2026 Impact high Products Firefox Fixed in Firefox 155 # CVE-2026-84117: Privilege escalation in Firefox for Android Reporter HiWorld Impact high References Bug 2053320 # CVE-2026-84118: Use-after-free in the JavaScript: GC component Rep
  • Security Vulnerabilities fixed in Firefox ESR 153.2 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Firefox ESR 153.2 Announced September 1, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 153.2 # CVE-2026-75874: Sandbox escape in the Remote Settings Client component Reporter crixer Impact high References Bug 2039972 # CVE-2026-84118: Use-after-free in the Jav
  • Security Vulnerabilities fixed in Thunderbird 155 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Thunderbird 155 Announced September 1, 2026 Impact high Products Thunderbird Fixed in Thunderbird 155 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or bro
  • Security Vulnerabilities fixed in Thunderbird 153.2 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Thunderbird 153.2 Announced September 1, 2026 Impact high Products Thunderbird Fixed in Thunderbird 153.2 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or
  • Security Vulnerabilities fixed in Firefox 155 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Firefox 155 Announced September 1, 2026 Impact high Products Firefox Fixed in Firefox 155 # CVE-2026-84117: Privilege escalation in Firefox for Android Reporter HiWorld Impact high References Bug 2053320 # CVE-2026-84118: Use-after-free in the JavaScript: GC component Rep
  • Security Vulnerabilities fixed in Firefox ESR 153.2 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Firefox ESR 153.2 Announced September 1, 2026 Impact high Products Firefox ESR Fixed in Firefox ESR 153.2 # CVE-2026-75874: Sandbox escape in the Remote Settings Client component Reporter crixer Impact high References Bug 2039972 # CVE-2026-84118: Use-after-free in the Jav
  • Security Vulnerabilities fixed in Thunderbird 155 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Thunderbird 155 Announced September 1, 2026 Impact high Products Thunderbird Fixed in Thunderbird 155 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or bro
  • Security Vulnerabilities fixed in Thunderbird 153.2 — Mozilla →Original publisher ↗Searchable text snapshot · Captured 26 Sep 2026Security Vulnerabilities fixed in Thunderbird 153.2 Announced September 1, 2026 Impact high Products Thunderbird Fixed in Thunderbird 153.2 In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or
04

Evidence and provenance

Published 1 Sept 2026 · Last source change 3 Sept 2026, 17:23 UTC · CWE-1021 · Improper Restriction of Rendered UI Layers or Frames

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-02
European sourceENISA EUVD · EUVD-2026-69087
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceCISA ADP
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  2. ENISA EUVD mappingEUVD-2026-69087 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-69087"}
    ENISA EUVD ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: mozilla.org/mfsa2026-82; added vendor advisory: mozilla.org/mfsa2026-85; 2 further additions.
    Before
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153
    After
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153 · vendor advisory: mozilla.org/mfsa2026-82 · vendor advisory: mozilla.org/mfsa2026-85 · 2 more references
    security@mozilla.org ↗
  4. SeveritySeverity changed from Unknown to Medium.
    Before
    Unknown
    After
    Medium
    NIST NVD ↗
  5. CVSS scoreCVSS score changed from not recorded to 6.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).
    Before
    not recorded
    After
    6.1 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
    NIST NVD ↗
  6. Vendor guidanceAuthoritative vendor guidance changed: added remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153; removed remediation: mozilla.org/mfsa2026-86.
    Before
    remediation: mozilla.org/mfsa2026-86
    After
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153
    CNA ↗
  7. Vendor guidanceAuthoritative vendor guidance changed: added remediation: mozilla.org/mfsa2026-86; removed remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153.
    Before
    remediation: bugzilla.mozilla.org/show_bug.cgi?id=2060153
    After
    remediation: mozilla.org/mfsa2026-86
    CNA ↗
  8. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-69087↗Vendor CSAF · SUSE Product Security Team↗Vendor advisory↗Vendor advisory↗Vendor advisory↗Vendor advisory↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-84139 · cve.blacktree.nl