Mozilla security advisory (AV26-1057)
Canada’s Cyber Centre urges updates for Firefox, Firefox ESR, and Thunderbird flaws fixed in October 2026 releases.
The Canadian Centre for Cyber Security issued advisory AV26-1057 on October 16, 2026, covering Mozilla vulnerabilities known as of October 13. Affected products are Firefox before 158, Firefox ESR before 153.5 and 115.43, and Thunderbird before 158 and 153.5. The centre points administrators to Mozilla Foundation Security Advisory 2026-107 and related Firefox ESR and Thunderbird advisories and recommends applying available updates. The notice does not list CVE identifiers or say the flaws are exploited.
- Advisory AV26-1057 was published on October 16, 2026.
- Firefox before 158 and ESR before 153.5 and 115.43 are affected.
- Thunderbird before 158 and 153.5 is also affected.
- No exploitation or CVE identifiers are stated.
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Serial number: AV26-1057
Date: October 16, 2026
As of October 13, 2026, Mozilla is affected by vulnerabilities in the following products:
- Firefox ESR
- Prior to 153.5
- Prior to 115.43
- Firefox
- Prior to 158
- Thunderbird
- Prior to 153.5
- Prior to 158
The Cyber Centre encourages users and administrators to review the provided web links and apply any necessary updates as they become available.
- Security Vulnerabilities fixed in Firefox 158 - Mozilla
- Mozilla Foundation Security Advisory 2026-107
- Security Vulnerabilities fixed in Firefox ESR 153.5 - Mozilla
- Security Vulnerabilities fixed in Thunderbird 158 - Mozilla
- Security Vulnerabilities fixed in Thunderbird 153.5 - Mozilla
- Mozilla Foundation Security Advisories - Mozilla
Text extracted automatically; images, tables and formatting may be missing. Original: https://cyber.gc.ca/en/alerts-advisories/mozilla-security-advisory-av26-1057