PAK File (Counter Strike Online)
Counter Strike Online's PAK file is a container format that stores the game's Resources files (models, sounds, sprites, etc.)
Counter Strike Online is using SNOW Stream Cipher for Encryption, with each section protected by a different key. Also, every entry is encrypted with its own unique Basekey Value
Extracting image of CSO PAK Archive
View image of CSO Pak
If you choose your model viewer Settings -> Configure in you can view the model while view the PAK. Also You can view Sprites too.
You can Also open PAK files on Windows File Explorer