#VU8631 Security restrictions bypass in Mozilla Firefox - CVE-2017-7820

Vulnerability identifier: #VU8631

Vulnerability risk: Low

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2017-7820

CWE-ID: CWE-264

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Mozilla Firefox
Client/Desktop applications / Web browsers

Vendor: Mozilla

Description
The vulnerability allows a remote attacker to bypass certain security restrictions.

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.

Mitigation
Update to version 56.0.

Vulnerable software versions

Mozilla Firefox: 48.0 - 55.0.3

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2017-21/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.