In brief: Hot on the heels of the FaceApp controversy comes another app that generates deepfakes and has managed to climb to the top of the free apps list in the Chinese iOS App Store. The company behind it has faced a wave of backlash after some users discovered that there are serious privacy concerns that come with all the fun, so it's now scrambling to revise its policies.

Zao is yet another deepfake app that allows you to swap your face and place it into several scenes from popular movies and TV shows. The app was released on Friday and has quickly overtaken all the other free apps in the entertainment section of the Chinese iOS App Store. Users were so excited about the experience that they generated over eight million views on Chinese microblogging site Weibo with Zao-generated content.

Even though it has a limited library of videos to choose from, the app seems to do a very quick and convincing job of overlaying your face on top of that of high-profile actors like Sheldon Cooper, Marilyn Monroe, and Leonardo DiCaprio. The app will ask for a series of pictures of your face to create more realistic deepfakes, but Twitter user Allan Xia says one picture is all it takes.

The app was developed by Chinese dating and live-streaming service Momo, who faced a lot of vitriol after some users combed through its 6,000 character privacy policy. According to Bloomberg, the company included a clause that says the developer gets a "free, irrevocable, permanent, transferable, and relicense-able" to the content generated by Zao users. This opened up a can of worms, with users review-bombing the app and Chinese media giving great exposure to the phenomenon.

Momo has since amended its user agreement to state that user-generated content inside the app will no longer be used for other purposes. Furthermore, deleting content in the app will also remove it from the company's servers. That said, China's E-Commerce Research Center asked the authorities to look into the matter, and WeChat has removed all links to the service.

This isn't the first time an app that uses machine learning sparked this much controversy. In July, Russian app FaceApp generated similar concerns over user privacy. The app has a convincing aging filter but its terms stated that by downloading the app, the user silently agrees that the developer can use their in-app data for commercial use without compensation. The company later clarified that it doesn't sell any user data and similarly offered the option to delete it on request.

Most users don't pay attention to the terms and conditions before using such services, even though it's been proven time and again that user agreements can contain clauses that affect privacy. What is even more worrisome is that researchers have found that many apps harvest your data even after you deny permissions.