MacOS users - Have you seen or done an update to Adobe Flash

 If you have seen this on your MacOS systems recently and have clicked through the update

You may have installed a backdoor malware that have infected Windows and Linux machines in the past. Flash is installed or updated along with the malware strain known as Snake, Turla, or Uroburos.
The malware install obtains the administrator password then is able to steal data like account usernames and passwords. The signing certificate was revoked, but a new certificate is a possibility now that the malware has been modified to infect MacOS. Users who ignore the certificate error will be infected.
 MalwareBytes can detect and remove the infection.  Use the Sun City Computer Club MALWARE HELP link then the MAC MALWARE PREVENTION/REMOVAL instructions or the Sun City Computer Club Help Center. I have seen this often the past few days on my MACs and it has been around on Windows and Linux in the past.
 It is good practice to have applications updated along with the operating system. If possible have application updates Ask before applying updates and DO NOT click through certificate errors.