Please check your AV again and exclude the 'Work' folder in this location - C:\Users\YourWindowsUserName\Cheathappens\ - or create a wildcard exclusion for the tmp file only like - ~CheathappensTrainer* - because the digits at the end of the file name are added randomly every time you start the trainer.
Also check your firewall if '~CheathappensTrainerxxxx.tmp' has access to the internet (if you authenticate your trainer online that is).
Excluding the Work folder did the trick! Thank you.
No, Stellaris did not receive any new DLC. What happened is that they rolled out a new version to 1.7.2 which was supposed to fix and enhance the multiplayer aspect of the game. This did not work for everyone so the game has been rolled back to 1.6.2.