If you have Firefox on your computer, you should update it right now. Mozilla has released security updates Firefox 67.0.3 and Firefox ESR 60.7.1 to fix a critical bug, which it says hackers are actively exploiting to take control of vulnerable systems. The US Cybersecurity and Infrastructure Security Agency also issued an alert urging users and system administrators to review Mozilla's security advisory and act accordingly -- in other words, update your browser.