What is CVE-2026-11799?

CVE-2026-11799 is a high-severity vulnerability in Mozilla Focus, classified under Cross-site Scripting. CVSS score: 7.5/10. Published 2026-06-09.

How severe is CVE-2026-11799?

High severity. CVSS v3 base score is 7.5 out of 10.

XSS in Mozilla Focus

CVE-2026-11799

UXSS in Focus for iOS / Klar Webkit navigation. This vulnerability was fixed in Focus for iOS 151.3.1 and Klar for iOS 151.3.1.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-06-09 · last modified 2026-07-23.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.002 (10.7th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 11th percentile — 10.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Mozilla Focus
Mozilla Focus For iOS — versions 151.3.1
Mozilla Klar
Mozilla Klar For iOS — versions 151.3.1

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-55/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-11799?: CVE-2026-11799 is a high-severity vulnerability in Mozilla Focus, classified under Cross-site Scripting. CVSS score: 7.5/10. Published 2026-06-09.
How severe is CVE-2026-11799?: High severity. CVSS v3 base score is 7.5 out of 10.