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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…
- 5.3MediumCVSS base score
- 1.2%Exploitation in 30 daysEPSS · top 32% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By mozilla
- 14 months later
· 14 months later
Published
- 6 years later
· 6 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.0 | Medium5.3 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 1.2% · top 32% of all CVEs (10 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Affected products
References
4
- 1039465 (opens in a new tab)vdb-entryx_refsource_SECTRACKx_transferred
- https://bugzilla.mozilla.org/show_bug.cgi?id=1378207 (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://www.mozilla.org/security/advisories/mfsa2017-21/ (opens in a new tab)x_refsource_CONFIRMx_transferred
- 101057 (opens in a new tab)vdb-entryx_refsource_BIDx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2017-16795 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2017-7820)Record last updated .