The pop up ads, promos, spin the wheel to get a 90% discount on item that are sold out or you don't want, Large t-shirts that would be tight on a toddler, and a million cheap knockoffs of US and European brands. Harbor Freight and Dollar Store rolled into one. They spam the shit out of you. And you have to install the mobile app and it nags you until you do.
I found the app so intrusive that I flattened my phone (full factory reset) and installed a pre-TEMU backup. I keep a second phone for banking and other financial activity and that's all I use it for. No texting or talking on it unless it is with a bank or brokerage. No other apps on it. So I wasnt worried about being compromised. I just don't trust the fucking Chinese.