Cross-site Scripting (XSS) Affecting firefox-esr package, versions <91.4.0esr-1


Severity

Recommended
0.0
medium
0
10

Snyk's Security Team recommends NVD's CVSS assessment. Learn more

Threat Intelligence

EPSS
1.35% (68th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-ECHOLATEST-FIREFOXESR-18169308
  • published22 Jul 2026
  • disclosed8 Dec 2021

Introduced: 8 Dec 2021

CVE-2021-43543  (opens in a new tab)
CWE-79  (opens in a new tab)

How to fix?

Upgrade Echo:latest firefox-esr to version 91.4.0esr-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.

Documents loaded with the CSP sandbox directive could have escaped the sandbox's script restriction by embedding additional content. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.

CVSS Base Scores

version 3.1