The Marvel Cinematic Universe is known for its tight security, as the universe grows thanks to new projects arriving in theaters and streaming with a Disney+ subscription. While the actors in the franchise are tasked with guarding its secrets, certain celebs like Tom Holland and Mark Ruffalo are known for accidentally spoiling things. Stranger Things star Sadie Sink is joining the MCU in Spider-Man: Brand New Day, and she's having a much easier time guarding spoilers than Holland.When Sadie Sink was confirmed for the new Spider-Man movie, theories and rumors started swirling about who she might play. Despite how many months have passed, fans still don't know who she'll be in the upcoming Marvel movie. During a recent interview with Nylon, she joked about how to guard spoilers, saying: You just don’t share the secret, it’s not that hard.Sometimes it's just that simple. Of course, Sink has lots of experience with this unique part of the job. She had to keep lots of secrets during her tenure on Stranger Things (streaming with a Netflix subscription), especially ahead of its fifth and final season. Stranger Things 4 ended with Max in a coma, and the Tony-nominated actress had to do press while not revealing what was going to happen to the beloved character. Now she's keeping mum about her mysterious role in Spider-Man: Brand New Day. Disney+: from $11.99 a month w/ ad-supported planDisney+ is the streaming home for the MCU and Spider-Man franchises. Plans start at $11.99 a month for its new ad-supported plan. Go ad-free and pay $18.99 a month or save 16% and pre-pay $189.99 for a year.View DealFans who spent years watching the Marvel movies in order will remember that Tom Holland has a bad track record with accidentally revealing spoilers. While Sink poked un at him in the above comment, later in the same interview she gushed about working with the Uncharted actor. In her words: It was interesting stepping into that space and being a little bit of an outsider in that way, but he could not have been more welcoming, and just the whole crew in general. He was just so relaxed and open, and I felt very at ease.Brand New Day is Tom Holland's fourth solo movie as Spider-Man, and his seventh overall appearance in the MCU. So his sense of ease around set makes a great deal of sense. Still, it's heartening to hear how comfortable he made Sadie Sink as she joined the massive shared universe. Now we just need to hear who she is playing already!Luckily our wait for answers is nearly over. Spider-Man: Brand New Day will hit theaters on July 31st as part of the 2026 movie release list. It's crunch time, so we'll have to see if any spoilers end up trickling out over the next few weeks.