The big-budget zombie film has seemingly come up against a series of obstacles, including a number of reshoots, raids on the set by Hungarian police, and rumours that star Brad Pitt is not on speaking terms with director Marc Forster.
However, in an interview with Collider, Fox rejected the notion that the film is troubled.
He said: "I think that the turmoil thing has been, it's one of those things that we live in a world these days where somebody can float an idea on the internet... and they can have no basis for expertise on that idea.
"They can be anyone. And they can have no basis in fact at all and suddenly it's become like a notion out there that World War Z is having problems.
"Everybody who I've spoken to that's seen the film - it rocks, dude; it's going to kick ass. And the only issue that I'm hearing with the film is that they want to work on the third act; the end of the film."
Fox's producers on Lost, Damon Lindelof and Drew Goddard, were brought in to re-write the third act. Fox suggested in the interview that this was due to the studio's wish to turn World War Z into a trilogy.
He claimed: "In the original script I always felt it was the perfect combination of a complete film on its own and yet at the same time left you going like, 'Oh my god, we need another instalment'.
"And so I think they're just really fine tuning that, and it might require some additional shooting to get it the way they want it."
World War Z is set for release in June 2013.
Watch Brad Pitt discuss World War Z with Digital Spy below: