Samsung has released software Update C900FDDU1AQC5 for Galaxy C9 Pro. The new update includes Android April Security patch.
Android April security patch includes fixes for vulnerabilities and exposures in the Android OS. The update also brings stability improvements, bug fixes and further improvements for performance.
Software Update C900FDDU1AQC5 for Galaxy C9 Pro will gradually roll out to everyone. However, you can also check manually for updates, Go to Settings > About device > System update.