Incorrect Authorization Affecting firefox-esr package, versions <91.3.0esr-1


Severity

Recommended
0.0
critical
0
10

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Threat Intelligence

EPSS
3.83% (89th percentile)

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  • Snyk IDSNYK-ECHOLATEST-FIREFOXESR-18169294
  • published22 Jul 2026
  • disclosed8 Dec 2021

Introduced: 8 Dec 2021

CVE-2021-38503  (opens in a new tab)
CWE-863  (opens in a new tab)

How to fix?

Upgrade Echo:latest firefox-esr to version 91.3.0esr-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream firefox-esr package and not the firefox-esr package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

CVSS Base Scores

version 3.1