"As BuzzFeed reports, leaked audio from more than 80 internal TikTok meetings reveals engineers working for ByteDance (TikTok's parent company) in China could see everything. In total, 14 statements from nine different TikTok employees confirmed access to the data by individuals located in China.
The evidence is quite damning, with US employees either not having permission to or knowledge of how to access US user data themselves. Instead, someone in China had to access it for them, with at least one ByteDance engineer in Beijing referred to as a "Master Admin.""
https://www.pcmag.com/news/leaked-audio-reveals-china-repeatedly-accessed-us-tiktok-user-data
"For years, TikTok has responded to data privacy concerns by promising that information gathered about users in the United States is stored in the United States, rather than China, where ByteDance, the video platform's parent company, is located. But according to leaked audio from more than 80 internal TikTok meetings, China-based employees of ByteDance have repeatedly accessed nonpublic data about US TikTok users — exactly the type of behavior that inspired former president Donald Trump to threaten to ban the app in the United States."
https://www.buzzfeednews.com/article/emilybakerwhite/tiktok-tapes-us-user-data-china-bytedance-access