Files labeled with "Skype UPD" or "High Quality" are common delivery methods for trojans or keyloggers.

For a legitimate experience, consider playing on servers with active admins or anti-cheat protection.

Reducing or removing the visual effects of grenades.

This is a legacy term from the mid-2000s and 2010s. Many "modders" would share updated (UPD) versions of their files via Skype groups or forums, claiming they were bypasses for updated anti-cheats. Features of the opengl32.dll Mod