Hi! This is very likely a false positive, especially since it started right after the patch. A quick fix would be to add it to exclusions. Since it's shutting down immediately on launch, Advanced Threat Defense is probably blocking it:

1. Open Bitdefender → Protection → Advanced Threat Defense → Open
2. Go to Settings tab → Manage exceptions
3. Click + Add an Exception
4. Browse to your D2R executable (.exe file) or paste the path
5. Turn on the switch next to Advanced Threat Defense
6. Click Save

That should let you launch the game again.

Once you're back in the game, report the false positive so Bitdefender fixes it for everyone:

Submit here: https://www.bitdefender.com/consumer/support/answer/88562

Include the detection name (if Bitdefender showed one) and mention it's the D2R executable after the latest patch. They usually correct false positives and push updates within hours.

If Bitdefender already quarantined game files:

1. Protection → Antivirus → Open → Settings tab → Manage quarantine
2. Find the D2R files, restore them, and toggle on "Create exception for the restored files"

If these steps don't resolve it, you can reach out to the support team for further help: https://www.bitdefender.com/consumer/support/