Hp 6950 Downgrade - Firmware [verified]
If the printer is connected via Wi-Fi or Ethernet, it may still silently download an update. The safest method is to keep the printer on a local network without internet access, or use USB-only printing.
For those still willing to take the risk, here's a step-by-step guide on how to downgrade your HP 6950 firmware: hp 6950 downgrade firmware