{"cve":"CVE-2021-38506","nvd":{"published":"2021-12-08T22:15:08.897","modified":"2026-06-17T04:02:14.803","status":"Modified","description":"Through a series of navigations, Firefox could have entered fullscreen mode without notification or warning to the user. This could lead to spoofing attacks on the browser UI including phishing. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N","score":4.3},"cwes":["CWE-1021"],"references":["https://bugzilla.mozilla.org/show_bug.cgi?id=1730750","https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html","https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html","https://security.gentoo.org/glsa/202202-03","https://security.gentoo.org/glsa/202208-14"],"products":["debian:debian_linux","mozilla:firefox","mozilla:firefox_esr","mozilla:thunderbird"],"source":"nvd","synced_at":"2026-10-19T21:25:41.256909649+00:00"},"epss":{"cve":"CVE-2021-38506","score":0.01507,"percentile":0.74403,"date":"2026-11-01"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}