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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.
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The Canadian Centre for Cyber Security issued advisory AV26-924 warning that Firefox releases before 156 and Firefox ESR releases before 115.41, 140.16, and 153.3 are affected. It urged users and administrators to review Mozilla's advisories and apply available updates.
Mozilla published security-vulnerability advisories for Firefox 156 and Firefox ESR 115.41, 140.16, and 153.3. The updates address unspecified vulnerabilities affecting earlier Firefox and ESR releases.
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Mozilla released security updates to address vulnerabilities in multiple Firefox products, including **Firefox 152**, **Firefox for iOS 152.0**, **Firefox ESR 140.12**, and **Firefox ESR 115.37**. The fixes were published through Mozilla Foundation Security Advisories **`MFSA 2026-56`** through **`MFSA 2026-59`**, with the Firefox for iOS update specifically covered in **`MFSA 2026-56`**. The Canadian Centre for Cyber Security issued alert **`AV26-604`** highlighting the advisories and warning that systems running versions prior to those releases remain affected. The agency urged users and administrators to review Mozilla’s guidance and apply the updates needed to remediate the disclosed flaws across supported desktop, mobile, and extended support browser versions.
Jun 30, 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
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