#NØØT_Security_Alerts 🚨 #ALERT — FIREFOX HIGH-SEVERITY SANDBOX ESCAPE AND SITE-ISOLATION VULNERABILITY October 13, 2026 DISCLOSED BY: Mozilla Security PRODUCT: Mozilla Firefox / Firefox ESR CVE: CVE-2026-109705 SEVERITY: HIGH — Mozilla assessment AFFECTED VERSIONS: Firefox releases preceding version 158 and affected Firefox ESR releases preceding 153.5. IMPACT: A use-after-free vulnerability involving incorrect boundary conditions in Firefox’s networking component can compromise browser sandbox and site-isolation protections. These protections help contain potentially malicious web content and separate security boundaries. Mozilla identifies both sandbox escape and site-isolation impact. EXPOSURE: The precise triggering conditions and exploit prerequisites have not been publicly established. EXPLOITATION STATUS: VENDOR-CONFIRMED HIGH-SEVERITY VULNERABILITY. No verified in-the-wild exploitation or independently confirmed public working PoC identified. Successful arbitrary code execution outside the browser sandbox has not been independently demonstrated. Forensic triage: Identify outdated Firefox and Firefox ESR installations. Review browser crashes, unexpected child processes and suspicious endpoint activity associated with untrusted web content. No confirmed CVE-specific malicious IOCs have been published. URGENT ACTION: Upgrade Firefox to version 158 or later. Upgrade affected Firefox ESR 153.x installations to ESR 153.5 or later. Restart browsers to activate updates. Prioritize enterprise-managed browsers and systems handling sensitive information. SOURCE: https://www.mozilla.org/en-US/security/advisories/mfsa2026-106/ FIREFOX ESR: https://www.mozilla.org/en-US/security/advisories/mfsa2026-108/ CONFIDENCE: HIGH — Mozilla’s October 13 advisories explicitly identify CVE-2026-109705 as a high-severity networking vulnerability involving sandbox escape, site isolation and use-after-free. UNVERIFIED — Active exploitation, working public exploit and victim compromise. #CyberSecurity #ThreatIntel #Firefox #Mozilla #BrowserSecurity #SandboxEscape