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Mozilla published advisory MFSA 2026-94 detailing security vulnerabilities corrected in Thunderbird 156. The associated Mozilla Bugzilla records, including bugs 2057121 and 2056051, are access-restricted, so technical vulnerability details and impact information are not publicly available in the referenced material.
Organizations using Thunderbird should upgrade deployed clients to version 156 through their normal software-management process and verify that older installations are remediated. Security teams should track Mozilla’s advisory for any later disclosure of CVE identifiers, affected configurations, severity ratings, or exploitation information.
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Mozilla published security advisory MFSA 2026-94 describing security vulnerabilities fixed in Thunderbird 156.
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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 security updates for **Firefox 154**, supported **Firefox ESR** branches, and **Thunderbird** to fix a broad set of vulnerabilities affecting desktop and mobile users. Government and vendor advisories said the updates address **3 critical** and **17 high-severity** flaws involving arbitrary code execution, privilege escalation, security restriction bypass, sandbox escape, site isolation failures, use-after-free conditions, and information disclosure. Firefox 154 also introduced product changes including expanded Local Access Network protections for WebSocket connections, while security notices from Canada and Italy urged organizations to review Mozilla bulletins and update affected installations. Tenable and downstream Linux advisories flagged the issue set as **critical** across Windows, macOS, and Slackware packages, with affected versions including Firefox releases prior to 154, multiple ESR builds before their patched versions, and Thunderbird releases prior to **140.14** or **154.0** depending on branch. Nessus coverage tied the fixes to numerous CVEs, including **`CVE-2026-74990`** as a scoring reference in several advisories, and highlighted specific Thunderbird issues such as a Remote Settings Client sandbox escape, a CanvasWebGL site isolation flaw, a DOM: Networking privilege escalation bug, and WebAssembly and garbage-collection use-after-free vulnerabilities. The recommended action across all notices was to upgrade Mozilla products to the latest patched versions immediately.
Aug 26, 2026
Mozilla released **Firefox 156** and **Firefox ESR 153.3** to address security vulnerabilities in its browser products. The Canadian Centre for Cyber Security advisory `AV26-924` identifies Firefox versions earlier than 156 and Firefox ESR versions earlier than **115.41**, **140.16**, and **153.3** as affected. Organizations should update standard Firefox deployments to version 156 and move ESR deployments to the applicable fixed release—115.41, 140.16, or 153.3. Administrators should review Mozilla’s associated security advisories, including `MFSA-2026-90` and `MFSA-2026-93`, and prioritize remediation across managed endpoints.
Sep 15, 2026