CVE-2018-12399: Canonical Ubuntu Linux

Medium severity, CVSS 4.3. EPSS: 1.6% chance of exploitation in the next 30 days.

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: version 14.04 only; version 16.04 only; version 18.04 only; version 18.10 only
• Mozilla Firefox: before 63.0 (fixed in 63.0)

Published 2019-02-28. Last modified 2026-06-17.