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Mozilla Firefox EUVDEUVD-2026-60659

| CVE-2026-74960 HIGH
Improper Access Control (CWE-284)
2026-08-18 mozilla GHSA-5r7x-fg3w-vcg2
Authentication Bypass Mozilla
8.1
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
8.1 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
vuln.today AI
9.3 CRITICAL

Site isolation bypass inherently crosses origin boundaries (S:C); UI:R and PR:N confirmed by network delivery requiring user page visit with no credential requirement.

3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
SUSE
HIGH
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

4
Analysis Generated
Aug 21, 2026 - 22:32 vuln.today
CVSS changed
Aug 21, 2026 - 20:22 NVD
8.1 (HIGH)
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 8.1
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Site isolation issue in the WebExtensions component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

AnalysisAI

Site isolation is broken in Firefox's WebExtensions component, allowing cross-origin access control boundaries to be violated. The CVSS vector (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N) places this as network-exploitable with high confidentiality and integrity impact, requiring only that a user visit an attacker-controlled page. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Attacker hosts malicious webpage
Delivery
Victim navigates to page in unpatched Firefox
Exploit
WebExtensions site isolation boundary bypassed
Execution
Cross-origin data from other tabs read or modified
Impact
Sensitive data (session tokens, page content) exfiltrated to attacker
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Vulnerability AssessmentAI

Exploitation Exploitation requires a user running Firefox prior to version 154 (or ESR prior to 140.14 / 153.1) to visit an attacker-controlled or malicious webpage - confirmed by the CVSS UI:R metric. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 8.1 score is driven by high C and I impact with no privilege requirement and low attack complexity, but the mandatory user interaction (UI:R) and absence of scope change (S:U) meaningfully constrain real-world risk. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker hosts a crafted webpage designed to trigger the site isolation flaw in Firefox's WebExtensions component. When a user running an unpatched Firefox version visits the page, the attacker's code exploits the access control gap to read or modify data belonging to other loaded origins - such as session tokens, page content, or form data from banking or enterprise applications open in adjacent tabs. …
Remediation Upgrade to Firefox 154 or later, Firefox ESR 140.14 or later, or Firefox ESR 153.1 or later, as confirmed by Mozilla across advisories mfsa2026-74 through mfsa2026-80 (https://www.mozilla.org/security/advisories/mfsa2026-74/). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, deploy the latest Firefox security patch to all endpoints using your system management platform and alert users to update any manually-managed installations. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container suse/kiosk/firefox-esr:140.14-75.12 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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EUVD-2026-60659 vulnerability details – vuln.today
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