20.12 patched flaws that allowed unauthorized network packets to cause controller major non-recoverable faults (MNRF).
RSLogix 5000 v20.12 was built during the Windows 7 era. However, modern deployment requires specific OS considerations: Operating System Compatibility Status Fully Supported Native environment, ideal stability. Windows 10 (64-bit) Supported with Caveats rslogix 5000 firmware 20.12