TikTok is meant, first and foremost, as an information operation platform, meaning that it can influence and it will introduce some information between small videos. If it controls the platform, it can can control the message. Once the program is installed in a phone, a tablet or whatever technology, they can remotely activate anything they want, because they control it.
It was found in a few types of similar applications that they had the reach to possibly turn on microphones, document pictures that were in the phone, and so on. It's in a minority of these applications that are out there, but that's the reality of playing with open sources, open platforms, that exist. They can reach and take the information they need.