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PatchSiren cyber security CVE debrief

CVE-2026-84127 Mozilla CVE debrief

Information disclosure vulnerability in Firefox for Android's WebExtensions component, fixed in Firefox 155. The vulnerability allows sensitive information to be disclosed, potentially impacting users who rely on WebExtensions for enhanced functionality. This issue was addressed with the release of Firefox 155, which includes security patches to mitigate the vulnerability. Users of Firefox for Android, particularly those who use WebExtensions, should be aware of this vulnerability and take steps to mitigate it by updating to the latest version. Operators of affected systems should assess their exposure and prioritize updates. Security teams should review compensating controls for exposed systems while remediation is scheduled and verified.

Vendor
Mozilla
Product
Firefox
CVSS
MEDIUM 4.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-01
Original CVE updated
2026-09-03
Advisory published
2026-09-01
Advisory updated
2026-09-03

Who should care

Users of Firefox for Android, particularly those who use WebExtensions, should be aware of this vulnerability and take steps to mitigate it. Operators of affected systems should assess their exposure and prioritize updates. Security teams should review compensating controls for exposed systems while remediation is scheduled and verified. Vulnerability management and security teams should monitor Firefox for Android for any suspicious activity and review WebExtensions for potential security risks.

Technical summary

The vulnerability is an information disclosure issue in the WebExtensions component of Firefox for Android. It was fixed in Firefox 155. The WebExtensions component in Firefox for Android is affected, and users should verify their versions and update to Firefox 155 or later. Defenders should review the official advisory for affected scope, severity, and vendor guidance. The vulnerability's impact on managed environments and potential exposure should be assessed. This issue highlights the importance of keeping software up-to-date to prevent potential security breaches.

Defensive priority

Apply Firefox updates to ensure the latest security patches are installed.

Recommended defensive actions

  • Apply Firefox updates to ensure the latest security patches are installed.
  • Monitor Firefox for Android for any suspicious activity.
  • Review WebExtensions for potential security risks.

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. Further investigation is needed to determine the full scope of the vulnerability. The WebExtensions component in Firefox for Android is affected, and users should verify their versions and update to Firefox 155 or later. Defenders should review the official advisory for affected scope, severity, and vendor guidance. The vulnerability's impact on managed environments and potential exposure should be assessed.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-84127 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-84127

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

  • CVE-2026-84127 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-84127

    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.