I've wanted to update my custom 1.12.2 Pack and then Avira came up with following message:

Thread blocked
Filename: supermartijn642corelib-1.1.1-forge-mc1.12.jar
Name of Thread: EXP/JAVA.Banload.VPDU.Gen
Type: Exploit
Location: (my User folder)
Status: moved to Quarantine.

And I would love to know why that is.
I've downloaded the file from CurseForge.

Antivirus software often has false positives with Java files. There is nothing malicious about my core library, in fact you see the code in this repository. If you want, you can even compile it yourself. CurseForge also already checks files for malware and VirusTotal also shows Avira as the only one to complain about the file: https://www.virustotal.com/gui/file/daa942615a82dce51ba0a77c5ca27dfc7a85bdf17c921d2a43227947cf370779

OK thanks for the answer I will whitelist the mod then.

Antivirus software often has false positives with Java files. There is nothing malicious about my core library, in fact you see the code in this repository. If you want, you can even compile it yourself.
CurseForge also already checks files for malware and VirusTotal also shows Avira as the only one to complain about the file:

https://www.virustotal.com/gui/file/daa942615a82dce51ba0a77c5ca27dfc7a85bdf17c921d2a43227947cf370779