Users of Mozilla Firefox should update immediately to Firefox 72.0.1 or Firefox ESR 68.4.1. This can be done through the browser’s built-in update feature but may need to be run manually, depending on set preferences. Always be mindful of clicking links from untrusted sources. Anti-virus products should be kept up-to-date on workstations and personal devices to help protect against any threats that may arise. EDR (endpoint detection and response) or MDR (managed detection and response) solutions can also help to spot threats before they begin to spread.
Source: https://www.mozilla.org/en-US/security/advisories/mfsa2020-03/, https://nakedsecurity.sophos.com/2020/01/09/browser-zero-day-update-your-firefox-right-now/