Marvel fans are being warned to stay away from social media after leaked footage from the upcoming "Avengers: Endgame" was found circulating online.

Walt Disney has kept the film shrouded in so much secrecy that even journalists and critics weren't permitted to see the film ahead of its premiere. "Endgame" opens April 26.

Those who have viewed the clip have called it "spoiler heavy." Screen shots, gifs, short clips, and detailed posts about what occurred during the clip are already surfacing on Twitter and Reddit.

Disney did not immediately respond to CNBC's request for comment. Marvel Studios appeared to address the incident Tuesday afternoon with a cryptic tweet featuring the hashtag #DontSpoilTheEndgame and a generic-sounding letter from the film's directors, Joe and Anthony Russo, imploring fans to keep quiet about the film's plot.

MARVEL TWEET

Dan Hill, CEO of Hill Impact, a marketing, lobbying and PR firm, said the incident could be an opportunity for Disney to respond in a smart way that keeps people talking, like leaking deleted scenes or bloopers from previous Marvel films.

"I think these are opportunities for companies to show their character in a way that maybe the public isn't used to seeing," he said. "It's an opportunity for Disney, which tends to be very buttoned up, to have some fun."

It is likely that the person behind the leak had clearance to view the footage.

Experts say a leak like this likely won't deter fans from going to see the film on its opening weekend.