{"action":"Upgrade firefox-esr to 91.4.0esr-1 or later.","affected":[{"fixed":"91.4.0esr-1","introduced":"0"}],"component":"firefox-esr","cve_ids":[],"ecosystem":"Debian","ecosystem_qualifier":"Debian:12","exploited":false,"fixed_versions":["91.4.0esr-1"],"id":"tcs_01M5NG1M6WS2DW1990QPRFAWS3","modified_at":"2026-10-23T18:04:16.664845214Z","published_at":"2021-12-08T22:15:09.890Z","references":["https://osv.dev/vulnerability/DEBIAN-CVE-2021-43542","https://security-tracker.debian.org/tracker/CVE-2021-43542"],"severity":{"label":"medium","score":6.5},"sources":[{"source":"osv","source_id":"DEBIAN-CVE-2021-43542","url":"https://osv.dev/vulnerability/DEBIAN-CVE-2021-43542"}],"summary":"Using XMLHttpRequest, an attacker could have identified installed applications by probing error messages for loading external protocols. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR <"}