I once 'informally advised' another Department Head that one of our Area Engineers was proposing to carry out an activity that was at best financially dubious and at worst illegal. The guy intervened and stopped the action - even sent me a 'thanks' email..
Unfortunately the person I 'dobbed in' was mates with my Chief Engineer who apparently ranted and raved when given the 'half story' by his mate.
Fortunately I was on leave at the time. When I returned from leave my boss advised me to keep a low profile. After some weeks I got a call to go visit the Deputy Chief Engineer, standing in his office the conversation went like this;
"You know why you are here?
"No idea"
"Well you upset XXXXXX (The Chief Engineer) over that issue about questionable financial matters."
" But ............."
"Don't say anything! just consider yourself reprimanded and we will let it rest there"
"OK, thanks,"
"OK - you can go............by the way it had the right outcome - but I did not say that"