CVE-2017-7820

CVE-2017-7820 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

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.

Frequently asked questions

What is CVE-2017-7820?
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.
How severe is CVE-2017-7820?
CVE-2017-7820 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2017-7820 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2017-7820?
CVE-2017-7820 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2017-7820?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2017-7820 published?
CVE-2017-7820 was published on 2018-06-11 and last updated on 2026-06-17.

References

Affected products (1)

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