CVE-2020-12423: Mozilla Firefox

High severity, CVSS 7.8. EPSS: 0.4% chance of exploitation in the next 30 days.

When the Windows DLL "webauthn.dll" was missing from the Operating System, and a malicious one was placed in a folder in the user's %PATH%, Firefox may have loaded the DLL, leading to arbitrary code execution. *Note: This issue only affects the Windows operating system; other operating systems are unaffected.* This vulnerability affects Firefox < 78.

Affected products

• Mozilla Firefox: before 78.0 (fixed in 78.0)

Published 2020-07-09. Last modified 2026-06-17.