CVE-2018-5121: Mozilla Firefox

Medium severity, CVSS 5.3. EPSS: 1.5% chance of exploitation in the next 30 days.

Low descenders on some Tibetan characters in several fonts on OS X are clipped when rendered in the addressbar. When used as part of an Internationalized Domain Name (IDN) this can be used for domain name spoofing attacks. Note: This attack only affects OS X operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 58.

Affected products

• Mozilla Firefox: up to and including 57.0.4

Published 2018-06-11. Last modified 2026-06-17.