add .exe extention to a normal jpg or zip file,and it’s reported with . unless file has zero bytes.
if you create a new text file,type something into it and saved,them rename it with .jpg.exe extentions,and it reported as heur.duel.extentions virus,too.
Since dual extensions are a popular malware trick, this detection is intentional.
The idea is that many users have their OS set to hide the extension of known file types. So if a malware author names their malware has vacation.png.exe, the OS will hide the .exe, and the file looks like a .png file to the user, and they may click it, not realizing they are about to run an unknown .exe.
If you do have a legitimate file with dual extensions, you can add it to the AV’s exclusions list.
if so,a defense+ warning for a non-virus dual extensions file is more better than a virus report.