AVG has quarantined firefox.exe. I have a screen shot. Now what?

Where did you get that Firefox? Is it an update/installer stub or the installed program? Does AVG display more information? ------- You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.