What makes you think it a virus? These type of cheats are very common and can be easly done using cheat engine. Although i aint downloading it lol just the fact that it to suspecious. But you shouldn't assume it a virus right away unless you were able to scan it.
So i will check it out once some one can verify it with a legit virus scan. And maybe if some one could verify what program they used to make the trainer also. Such as if it is cheat engine own personal trainer maker or if he coded in a different language.
Btw it not a glitch. And it is Client sided. So nobody else can see except for you. Your just changing the ID of your character with another NPC. Which cause a grafic change on your screen. But to everybody else screen you still look like you.