These links take you to the latest of each firmware. However, if your system is operating normally it is not worth the risk to update firmware that is 10 years old anyway. Yuneec updates have never been famous for reliability. Many functional kits were turned into useless paperweights in attempts to install updates that had no real benefit to start with.
If your camera is a CGo3:
Note there are two versions of the "latest" CGo3 firmware. If you install the wrong one the camera is often permanently bricked. Let us know if you need help identifying which version of CGo3 you have. cgo3gb_2.4.00_A_firmware.bin - used for cameras with Open IMU. cgo3_3.0.04_A_firmware.bin - used for cameras with Boxed IMU.