fox guarding (the) henhouse

Translations
лиса сторожит курятник
Putting the CEO's son in charge of auditing is like the fox guarding the henhouse.
Поставить сына генерального директора во главе аудита - это как если бы лиса сторожила курятник.
Definitions
A situation in which someone is put in charge of something but has a conflict of interest or is likely to exploit the position for their own benefit, similar to putting a fox in charge of guarding hens, which it would normally prey upon.