CVE-2017-7820

Severity: medium (CVSS 5.3 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2018-06-11 · updated 2026-06-17

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.

Affected products

Mozilla Firefox: through 55.0.3

References

http://www.securityfocus.com/bid/101057
http://www.securitytracker.com/id/1039465
https://bugzilla.mozilla.org/show_bug.cgi?id=1378207
https://www.mozilla.org/security/advisories/mfsa2017-21/
http://www.securityfocus.com/bid/101057
http://www.securitytracker.com/id/1039465
https://bugzilla.mozilla.org/show_bug.cgi?id=1378207
https://www.mozilla.org/security/advisories/mfsa2017-21/

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