It really depends on the bug? If it is a bug that causes your program to crash or return obviously invalid output then it's probably OK to fix it. But if the 'b

It really depends on the bug? If it is a bug that causes your program to crash or return obviously invalid output then it's probably OK to fix it. But if the 'bug' does something useful that just happens to be undocumented or contradicts the documentation, then you need to be a lot more careful about 'fixing' it. Especially if it's clear that lots of people are relying on that bug as a feature.