Safe from what? Always assume that an exit node is compromised. Never run unencrypted and unauthenticated traffic over it. There used to be these password sniffing experiments run over exit nodes, which always caught surprisingly many logins. Don't do it.

That doesn't mean traffic can be deanonymized. Tor as a whole isn't compromised in any meaningful sense even if the exit nodes are. Large parts of the original white paper concerns this.