Hackers from Anonymous told The NYT they had created fake accounts on Trump's Truth Social site.
On a fake Trump account, they posted a photo of a defecating pig, the publication reported.
"We had a fun time trolling it to high heaven," one of the hackers said.
Former President Donald Trump's upcoming social-media site, Truth Social, was hacked just a few hours after the announcement of its launch.
Hackers claiming affiliation with the group Anonymous created fake accounts for Trump and his former aide Steve Bannon on Truth Social, the network that Trump announced Wednesday, The New York Times reported. Fake accounts were also set up in the names of conspiracy theorist Ron Watkins and Twitter CEO Jack Dorsey.
The hackers posted a picture of a defecating pig on an account with the handle @donaldjtrump, the publication reported, with screenshots shared on Twitter.
The hackers told The Times the hack was part of their "online war against hate."
Trump said on Wednesday that he was creating Truth Social through his new company, Trump Media & Technology Group (TMTG), "to stand up to the tyranny of Big Tech."
TMTG said that the site would open to invitees in November and to the public in the first quarter of 2022. The app is currently available for pre-order in Apple's App Store, and people are able to join a waiting list.
That alone was enough for Anonymous hackers to get access to the prerelease version of the Twitter-like app, Aubrey Cottle, a hacker affiliated with Anonymous, told The Times. The publication said it viewed screenshots verifying the hackers' claims, and reported that hackers gained access within two hours of Trump announcing the site.
"We had a fun time trolling it to high heaven," Cottle said.
He told the publication that hackers then posted memes from fake accounts for public figures including Trump and former Vice President Mike Pence.
Other people have pointed out the beta site's vulnerability, too.
Daily Dot reporter Mikael Thalen also said that he was able to get access to the site and create an account with the handle @donaldtrump, while Washington Post reporter Drew Harwell said he created an account registered as @mikepence, which was later blocked by the site.
Within hours of the site's announcement, TMTG's app developers banned people from making new accounts and closed the beta site.