Mozilla security advisory (AV26-976)
Canada's Cyber Centre urges updates for Firefox before 157 and three Firefox ESR branches after Mozilla security fixes.
On September 29, 2026, the Canadian Centre for Cyber Security issued advisory AV26-976 warning that Mozilla products are affected by security vulnerabilities. Listed builds are Firefox versions before 157 and Firefox ESR versions before 153.4, 140.17, and 115.42. The centre urges users and administrators to review Mozilla's advisories and apply available updates. The bulletin does not name CVE identifiers or say the flaws are being exploited.
- Advisory AV26-976, dated September 29, 2026, covers Firefox and Firefox ESR.
- Affected builds are Firefox before 157 and ESR before 153.4, 140.17, and 115.42.
- The notice names no CVE identifiers and does not report active exploitation.
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Serial number: AV26-976
Date: September 29, 2026
As of September 29, 2026, Mozilla is affected by vulnerabilities in the following products:
- Firefox ESR
- Versions prior to 153.4
- Versions prior to 140.17
- Versions prior to 115.42
- Firefox
- Versions prior to 157
The Cyber Centre encourages users and administrators to review the provided web links and apply any necessary updates as they become available.
Text extracted automatically; images, tables and formatting may be missing. Original: https://cyber.gc.ca/en/alerts-advisories/mozilla-security-advisory-av26-976