CVE-2019-9812: Mozilla Firefox

Critical severity, CVSS 9.3. EPSS: 1.5% chance of exploitation in the next 30 days.

Given a compromised sandboxed content process due to a separate vulnerability, it is possible to escape that sandbox by loading accounts.firefox.com in that process and forcing a log-in to a malicious Firefox Sync account. Preference settings that disable the sandbox are then synchronized to the local machine and the compromised browser would restart without the sandbox if a crash is triggered. This vulnerability affects Firefox ESR < 60.9, Firefox ESR < 68.1, and Firefox < 69.

Affected products

• Mozilla Firefox: before 60.9 (fixed in 60.9); before 69.0 (fixed in 69.0); from 61.0, before 68.1 (fixed in 68.1)

Published 2020-01-08. Last modified 2026-06-17.