PlankFilza is a modified version of the Filza file explorer utility for iOS 14. This version of Filza utilizes the cicuta_virosa exploit, which ModernPwner released four days ago.      
Essentially, it is just a file manager that works on non-jailbroken iOS devices. Once installed, it gives you limited read/write permissions to the iOS filesystem.
In its current iteration, you can read files from any directory but write only to the /var and /tmp locations.