XSLT Markup Bypass Vulnerability in Firefox ESR, Firefox, and Thunderbird

CVE-2021-4140 · CRITICAL Severity

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

It was possible to construct specific XSLT markup that would be able to bypass an iframe sandbox. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.

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