Firefox is a popular internet browser from Mozilla which is a great alternative to Microsoft Edge or Google Chrome. If you use it, however, you should update it immediately.
The Dept. of Homeland Security has issued a warning that there is a bad security flaw within the browser which could allow an attacker to install malicious code on a computer. They also have said that attacks on this flaw are happening.
The good news is that the flaw has been patched, and all you need to do is update Firefox. To do so, just go to Help, then About Firefox. There you'll see if you have the latest version or if an update is needed.