That's an honest question. He's widely assumed to be corrupt, to have a large amount of money personally, and an enormous amount more at 1+ removes held by people connected to him. There's no sign that he intends to leave power, which means he can store plenty of it without any paperwork at all - just an implicit "you'll use this as I ask if I ever do ask".
But he's also virtually untouchable, and his wealth-hiding seems to be less "no one can find it" and more "no one can prove it so undeniably that it becomes inconvenient". I'm not convinced there's anything 'leakable' that would be particularly important.
Has any wealthy or powerful persons finances ever been leaked before (outside of the Panama leaks)? Or is this just popular political position to make regardless of relevance to reality?
There is a very big difference between the security of peoples financial and tax records compared to say... some 70yr olds private email account stored on a poorly secured home server. Not to mention someone like Putin would likely have layers of shell companies and layers of diversions where it wouldn't be of much use.
People like to pretend Wikileaks can hack and leak anything, and it's merely a political descision for them on who gets hacked. But they are merely a platform for leaks, publishing almost exclusively either opportunistic hacks (Manning leaks) or low hanging fruit (personal email servers) they recieve from other people. They don't direct a network of hackers to do their politically motivated bidding.
