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CVE-2026-11799 Mozilla CVE debrief

CVE-2026-11799 is a UXSS (User Experience Security issue, potentially leading to Spoofing) vulnerability affecting Focus for iOS and Klar for iOS. The issue is related to Webkit navigation. The vulnerability was fixed in Focus for iOS 151.3.1 and Klar for iOS 151.3.1. The CVSS score for this vulnerability is 7.5, indicating a HIGH severity level. The vulnerability was published on [cve-org](https://www.cve.org/CVERecord?id=CVE-2026-11799) on 2026-06-09T21:17:03.410Z and modified on 2026-06-10T20:14:36.697Z. Additional details can be found on [nvd](https://nvd.nist.gov/vuln/detail/CVE-2026-11799).

Vendor
Mozilla
Product
Focus for iOS
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-09
Original CVE updated
2026-06-17
Advisory published
2026-06-09
Advisory updated
2026-06-17

Who should care

Users of Focus for iOS and Klar for iOS, particularly those using versions prior to 151.3.1, should update their applications to the latest version to mitigate this vulnerability.

Technical summary

The vulnerability, identified as CVE-2026-11799, is a UXSS issue in Focus for iOS / Klar Webkit navigation. It has been assigned a CVSS score of 7.5, indicating a HIGH severity level. The issue was fixed in Focus for iOS 151.3.1 and Klar for iOS 151.3.1. For more technical details, refer to [ref-4](https://bugzilla.mozilla.org/show_bug.cgi?id=1975667) and [ref-5](https://www.mozilla.org/security/advisories/mfsa2026-55/).

Defensive priority

HIGH

Recommended defensive actions

  • Update Focus for iOS to version 151.3.1 or later.
  • Update Klar for iOS to version 151.3.1 or later.

Evidence notes

The vendor for this vulnerability is listed as Unknown Vendor, but evidence suggests a connection to Mozilla.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-11799 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-11799

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-11799 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-11799

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.