CVE-2018-12399

Severity: medium (CVSS 4.3 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-02-28 · updated 2026-06-17
Weakness: CWE-287

Description

When a new protocol handler is registered, the API accepts a title argument which can be used to mislead users about which domain is registering the new protocol. This may result in the user approving a protocol handler that they otherwise would not have. This vulnerability affects Firefox < 63.

Affected products

Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 18.10
Mozilla Firefox: before 63.0 — fixed in 63.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 63.0. Check the vendor advisory for mitigations.

References

http://www.securityfocus.com/bid/105721
http://www.securitytracker.com/id/1041944
https://bugzilla.mozilla.org/show_bug.cgi?id=1490276
https://usn.ubuntu.com/3801-1/
https://www.mozilla.org/security/advisories/mfsa2018-26/
http://www.securityfocus.com/bid/105721
http://www.securitytracker.com/id/1041944
https://bugzilla.mozilla.org/show_bug.cgi?id=1490276
https://usn.ubuntu.com/3801-1/
https://www.mozilla.org/security/advisories/mfsa2018-26/

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