Out of all the actors that have ever appeared in the Marvel Cinematic Universe, there are just two who stand out for being the worst at keeping secrets: Mark Ruffalo, who plays the Hulk; and Tom Holland, who played Spider-Man. The latter recently appeared at a panel at FanX 2019 and was asked about who he believed to be the "biggest spoiler."
Holland was quick to defend himself, exclaiming, "I haven't spoiled anything!" to which certain members of the audience openly disagreed. The actor then reasoned, "I've spoiled a few things, but Mark Ruffalo said that everybody dies at the end of Infinity War," referring to a 2017 Good Morning America interview with Mark Ruffalo and Don Cheadle. Holland continued, "the thing is -- no one took him seriously. Like, if I had said that, everyone'd be like, 'yeah, it probably happens.'"
The actor then raised another good point, "Mark live-streamed the first 20 minutes of [Thor: Ragnarok] by accident. I didn't do that." As to the question of the worst spoiler, Holland concluded by saying, "I have to say Mark is." Interestingly, he also revealed that he challenged a journalist to make a list of everything he had spoiled, unfortunately, the results are not in yet.
The former MCU actor has been known to give away minor details, as he did with Spider-Man: Homecoming, but, as he said, he has never given away details as substantial as the ones Ruffalo has unintentionally divulged to the public. Regardless, Holland does have a reputation for being untrustworthy with film secrets, so much so that he reportedly wasn't allowed the script for Avengers: Infinity War at any point.
All that being said, Marvel Studios president Kevin Fiege has explained that -- despite a few slip-ups here and there -- the young actor was ultimately able to keep his lips sealed when it came to larger film spoilers. Following the collapse of the Sony-Marvel Studios partnership, it appears that Tom Holland won't have to worry about spoilers at all anymore, much to the chagrin of MCU Spider-Man fans everywhere.