Mozilla security advisory (AV26-726)
Serial number: AV26-726 Date: July 21, 2026 On July 21, 2026, Mozilla published security advisories to address vulnerabilities in the following products. Included were critical updates for the following: Firefox ESR – versions prior to 140.13 Firefox ESR – versions prior to 115.38 Firefox – versions prior to 153 The Cyber Centre encourages users and administrators to review the provided web links and apply the necessary updates. Mozilla Foundation Security Advisory 2026-70 Mozilla Foundation Security Advisory 2026-69 Mozilla Foundation Security Advisory 2026-68 Mozilla Security Advisories
CSIRTS triage
- What
- Vulnerabilities have been fixed in Firefox and Firefox ESR products.
- Who is affected
- Users and administrators of Firefox ESR versions prior to 140.13 and 115.38, and Firefox versions prior to 153.
- Urgency
- Remediation is critical due to the severity of the vulnerabilities.
- Action
- Apply the necessary updates to the affected Firefox products.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://cyber.gc.ca/en/alerts-advisories/mozilla-security-advisory-av26-726
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