Everyone is back at work and starting to use computers on our smallest network which has Internet access through a rather old Linksys router. Two systems were left on and screen-locked over the extra long weekend. There does not appear to have been any Internet access interruption in our absence. A Firefox browser on one system was left pointing to a commonly used web site: https://www.yahoo.com/. This Yahoo web page was not displayed when the user unlocked the screen and brought up the browser from the task bar. Instead, a site located at the link https://gaibacoupontec.com was displayed with a message indicating that there was an urgent Firefox update required. There was a button to download and to install the update. I killed the Firefox browser rather than getting rid of it with the X in the upper right hand corner. This event has the aroma of an unwanted cyber intrusion, which is why I killed the browser. I have also copied and stored the full URL displayed in the browser, but have only included the first part "https://gaibacoupontec.com" here so as not to tempt anyone to risk access. Is it possible that a new Firefox flaw has been detected and is being exploited for malicious purposes?