Multiple vulnerabilities in Mozilla Firefox products
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Multiple vulnerabilities in Firefox and Firefox ESR allow remote code execution, privilege escalation, and denial of service.
CERT-FR has published an advisory covering multiple vulnerabilities affecting Mozilla Firefox and Firefox ESR. The affected versions include Firefox versions prior to 153, Firefox ESR versions prior to 115.38, and Firefox ESR versions prior to 140.13. These vulnerabilities enable attackers to execute arbitrary code remotely, escalate privileges, cause denial of service, bypass security policies, and compromise data confidentiality. The advisory references three Mozilla security bulletins (mfsa2026-68, mfsa2026-69, mfsa2026-70) published on 21 July 2026 and lists 65 distinct CVE identifiers documenting specific flaws across the affected products. Defenders should apply updates to affected Firefox and Firefox ESR installations immediately, as the vulnerability set includes high-impact remote code execution issues.
Mentioned in this report
Detection guidance
Firefox Spawning Command Shell or Scripting Interpreter
Firefox or Firefox ESR spawning a shell, scripting host or LOLBin child process, a common post-exploitation sign of a browser RCE or sandbox escape. Auto-generated starting point — validate and tune in your environment before deploying. IOC matches can false-positive on shared infrastructure and decay as adversary infrastructure rotates.
title: Firefox Spawning Command Shell or Scripting Interpreter
description: Detects firefox.exe starting a command shell, scripting host or common
living-off-the-land binary. Normal Firefox browsing does not launch these, so this
pattern is a behavioural indicator of client-side exploitation (memory corruption
RCE or sandbox escape) rather than a specific CVE or payload. The advisory describes
no concrete post-exploitation behaviour, so this is a generic exploitation-consequence
detection.
tags:
- attack.execution
- attack.t1203
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage|endswith: \firefox.exe
Image|endswith:
- \cmd.exe
- \powershell.exe
- \pwsh.exe
- \wscript.exe
- \cscript.exe
- \mshta.exe
- \rundll32.exe
- \regsvr32.exe
- \certutil.exe
- \bitsadmin.exe
- \msiexec.exe
condition: selection
falsepositives:
- Native messaging hosts or browser extensions (for example password managers or enterprise
SSO helpers) that launch cmd.exe or powershell.exe
- Users opening downloaded scripts or installers directly from the Firefox download
panel
level: medium
id: 08d61fad-7b8b-52a4-b3e9-a0288239565a
status: experimental
author: Vorant
references:
- https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-0910
Behavioural rules are generated from public reporting — validate in your environment before deploying.
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-0910
What this brief leaves out
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