Fans questioned the safety of the event on social media.
Kendall Jenner celebrated her 25th birthday at a Halloween-themed bash on Saturday night. The model, who turns 25 on Tuesday, hosted the party at Harriet's Rooftop atop 1 Hotel in West Hollywood, with celebs like Justin Bieber, The Weeknd and Doja Cat on the guest list.
Hailey Bieber, Kanye West and Kim Kardashian West, Scott Disick, Kylie Jenner, Travis Scott, Jaden Smith, Paris Hilton, Justine Skye, Quavo, Winnie Harlow and Saweetie were just some of the other stars in attendance.
ET has learned every person entering the venue -- both employees and party guests -- had to have a rapid COVID-19 test with a negative result on site before going upstairs to the party.
The stars went all out with their costumes -- Kendall got Pamela Anderson's stamp of approval on her Barb Wire get-up, while The Weeknd spent six hours getting into his Nutty Professor costume -- but some fans were not impressed.
Several users took to social media, questioning whether attendees followed CDC guidelines like social distancing and wearing masks amid the coronavirus pandemic.
Kendall's party comes soon after Kim hosted her own birthday bash. The mom of four flew her closest friends and family to a private island to celebrate her 40th birthday last month.
Kim also received backlash for the party -- which included 20 to 25 attendees -- as fans found the social media posts insensitive to those suffering right now amid the pandemic.
Khloe Kardashian addressed the criticism during her appearance on The Ellen DeGeneres Show last week, calling Kim's party "so special."
"I don't really know the extent of it," Khloe admitted. "But this year is a frustrating year. I get it. I think there's so many frustrations going on for everybody. But also it's her 40th. This is something that she wanted to do for us. It was such a nice thing."
"Being there with all the precautions that we took and being there and how grateful everyone was for the tourism aspect of it," she said. "So many people said that we were their first party of guests that they've had in months and what it's done for them to be able to pay their bills or to be able to do stuff for their family, just hearing those messages when we were there, we felt really good and we felt so safe. We did it in the safest way I could imagine someone doing it."
See more in the video below.