> What’s the specific national security issue

The app is owned and controlled by the Chinese Communist Party. Basically the equivalent of a Chinese citizen using a CIA-controlled app to get their news. It's a very bald-faced security threat.

Furthermore, China has explicitly banned any American social media from the Chinese market for years. They know it's dangerous letting foreign nationals control your narrative, probably because they've been exploiting social media for years.

Oh, and there's also the electoral controversy: https://kyivinsider.com/russia-and-china-just-rigged-romania...