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Mozilla issued fixes for multiple vulnerabilities affecting Firefox, Firefox ESR, and Thunderbird, prompting publication of dCERT advisories 2026-0976 and 2026-1206. The advisories indicate that the flaws impact both Mozilla’s mainstream browser releases and its email client, with the later notice expanding coverage to include Firefox ESR alongside Firefox and Thunderbird.
While the advisories do not provide a public synopsis of the underlying bugs, the coordinated notices show ongoing remediation for several security issues across Mozilla products. Organizations using Firefox, Firefox ESR, or Thunderbird should treat the updates as security-relevant and prioritize deployment through normal patch management processes to reduce exposure to unpatched client-side vulnerabilities.
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2 events from the most recent confirmed update back to the earliest known activity.
dCERT issued advisory 2026-1206 covering multiple vulnerabilities affecting Mozilla Thunderbird, Firefox ESR, and Firefox. This appears to be a separate advisory from the earlier April notice, expanding coverage to Firefox ESR as well.
dCERT issued advisory 2026-0976 covering multiple vulnerabilities affecting Mozilla Firefox and Thunderbird. The reference does not provide technical details or affected versions beyond the product names.
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Mozilla released security advisories addressing vulnerabilities in **Firefox** and **Firefox ESR**, prompting the Canadian Centre for Cyber Security to urge organizations and users to apply updates. The affected versions included Firefox releases prior to `149`, Firefox ESR releases prior to `115.34`, and Firefox ESR releases prior to `140.9`, according to the earlier advisory. A subsequent Mozilla advisory issued additional fixes for the same product lines, affecting Firefox versions prior to `149.0.2`, Firefox ESR versions prior to `115.34.1`, and Firefox ESR versions prior to `140.9.1`. The Canadian Centre for Cyber Security described the notices as vendor patch and mitigation guidance and advised administrators to review Mozilla’s bulletins and deploy the necessary updates across exposed systems.
Jun 29, 2026
Mozilla released **Firefox 150** and updated **Firefox ESR** branches to address multiple security vulnerabilities, prompting downstream advisories from Debian and the Canadian Centre for Cyber Security. The fixes cover Firefox versions prior to `150`, Firefox ESR versions prior to `140.10` and `115.35`, and include vulnerabilities tracked as **CVE-2026-6768**, **CVE-2026-6784**, **CVE-2026-6785**, and **CVE-2026-6786**. **CVE-2026-6768** was described as a mitigation bypass in Firefox’s `Networking: Cookies` component and was assigned a **CVSS 9.8** score, indicating potentially severe impact if left unpatched. Mozilla also shipped related security fixes in **Thunderbird 150**, which uses Firefox’s web engine and addressed issues including a clickjacking and information disclosure flaw referenced in the Firefox advisories. Alongside the security patches, Mozilla’s releases included broad product updates such as privacy and platform changes in Firefox and improved encrypted-message search and OpenPGP features in Thunderbird. Government and Linux distribution advisories urged users and administrators to review Mozilla’s bulletins and apply the latest browser and mail client updates promptly.
Jun 29, 2026
Mozilla released **critical security updates** for Firefox and Firefox ESR, and the Canadian Centre for Cyber Security urged organizations and users to apply them promptly. The affected versions are **Firefox prior to 153**, **Firefox ESR prior to 140.13**, and **Firefox ESR prior to 115.38**. The advisories were issued as patch guidance rather than a confirmed report of active exploitation, but they address vulnerabilities serious enough to warrant immediate attention. Reporting on the release says Firefox 153 and the updated ESR branches include a broad set of fixes, with one source citing **216 vulnerabilities** resolved. The update also addresses flaws tracked as **`CVE-2026-16411`** and **`CVE-2026-16360`**, alongside multiple memory-safety issues described as potentially exploitable for **arbitrary code execution**. In addition to security remediation, the browser release includes privacy and isolation improvements such as stronger local network access protections and changes to cookie handling behavior.
Jul 21, 2026