{"id":"CVE-2017-7820","url":"https://www.cyber-defence.io/tools/cve/CVE-2017-7820","generatedAt":"2026-10-29T01:52:07.429Z","title":"The \"instanceof\" operator can bypass the Xray wrapper mechanism.","description":"The \"instanceof\" operator can bypass the Xray wrapper mechanism. When called on web content from the browser itself or an extension the web content can provide its own result for that operator, possibly tricking the browser or extension into mishandling the element. This vulnerability affects Firefox < 56.","published":"2018-06-11T21:29:11.000Z","lastModified":"2026-06-17T01:25:17.000Z","status":"Modified","sourceIdentifier":"security@mozilla.org","cvss":{"version":"3.0","score":5.3,"severity":"MEDIUM","vector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"cwe":[],"affected":["mozilla/firefox"],"epss":{"score":0.01163,"percentile":0.67087,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (1.16%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"http://www.securityfocus.com/bid/101057","tags":["Third Party Advisory","VDB Entry"],"source":"security@mozilla.org"},{"url":"http://www.securitytracker.com/id/1039465","tags":["Third Party Advisory","VDB Entry"],"source":"security@mozilla.org"},{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1378207","tags":["Exploit","Issue Tracking"],"source":"security@mozilla.org"},{"url":"https://www.mozilla.org/security/advisories/mfsa2017-21/","tags":["Vendor Advisory"],"source":"security@mozilla.org"},{"url":"http://www.securityfocus.com/bid/101057","tags":["Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.securitytracker.com/id/1039465","tags":["Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugzilla.mozilla.org/show_bug.cgi?id=1378207","tags":["Exploit","Issue Tracking"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.mozilla.org/security/advisories/mfsa2017-21/","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2017-7820","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}