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Mozilla Firefox CVE-2026-8964

| EUVDEUVD-2026-30915 HIGH
User Interface (UI) Misrepresentation of Critical Information (CWE-451)
2026-05-19 mozilla GHSA-x37c-vm4v-4wvx
Information Disclosure Mozilla
High
Disputed · 7.5 Vendor: mozilla
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Severity by source

Sources disagree (Low–High)
Vendor (mozilla) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
vuln.today AI
4.3 MEDIUM

Remote web content with low complexity and no auth (AV:N/AC:L/PR:N), but spoofing requires the victim to view/act on the UI (UI:R) and only deceives the user (I:L, C/A:N).

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
3.4 LOW
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

3
Analysis Generated
Jul 23, 2026 - 17:40 vuln.today
CVE Published
May 19, 2026 - 12:30 nvd
UNKNOWN (no severity yet)
CVE Published
May 19, 2026 - 12:30 cve.org
HIGH 7.5

DescriptionCVE.org

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

AnalysisAI

Content spoofing in Mozilla Firefox (versions prior to 151) lets a remote web page abuse the Popup Blocker component to misrepresent UI or origin information to the user, classified under CWE-451 (UI misrepresentation of critical information). No authentication is required (PR:N) and Mozilla has shipped a fix in Firefox 151. There is no public exploit identified at time of analysis, exploitation is rated 'none' by CISA SSVC, and EPSS is negligible at 0.02% (7th percentile).

Technical ContextAI

The flaw lives in Firefox's Popup Blocker, the browser subsystem that decides whether script-initiated window.open() / popup requests are shown or suppressed. CWE-451 (User Interface Misrepresentation of Critical Information) is the root-cause class: the browser presents content or window context in a way that misleads the user about its true source or nature - the classic 'spoofing' failure mode where a security-relevant UI cue does not reflect reality. The affected code is Firefox's Gecko-based popup handling; the CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* confirms the Firefox application (all pre-fix versions) as the affected product. Because the manipulation happens entirely in rendered/displayed content, the CVSS records integrity impact (I:H) with no confidentiality or availability effect.

RemediationAI

Vendor-released patch: Firefox 151 - upgrade all Firefox installations to 151 or later, which is the definitive fix. Enterprises running the Extended Support Release or vendor-packaged builds (SUSE, Red Hat) should apply the corresponding patched package once published by their distribution rather than assuming the mainline 151 build number. Consult Mozilla advisories https://www.mozilla.org/security/advisories/mfsa2026-46/ and https://www.mozilla.org/security/advisories/mfsa2026-50/ for the authoritative fixed-version mapping. No practical in-product workaround exists for a popup-blocker spoofing flaw short of patching; as an interim compensating control you can push browser policy to block or heavily restrict popups and script-opened windows (reducing the attack surface but potentially breaking legitimate sites that rely on popups), and reinforce user awareness that popup/window content cues may be untrustworthy. Given the low exploitation risk, standard patch-cycle deployment is appropriate rather than emergency out-of-band action.

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP7 Fixed

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CVE-2026-8964 vulnerability details – vuln.today
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