Zao went viral in China this weekend for its realistic face-swapping videos, but after controversy about its user policy, WeChat restricted access to the app on its messaging platform.

Users can still upload to WeChat videos they created with Zao, but if they try to download the app or send an invite link to another WeChat user, a message is displayed that says “this web page has been reported multiple times and contains security risks. To maintain a safe online environment, access to this page has been blocked.”

Developed by a unit of Momo, one of China’s most popular dating apps, Zao creates videos that replace the faces of celebrities in scenes from popular movies, shows and music videos with a selfie uploaded by the user.

The app, currently available only in China, went viral as users shared their videos through WeChat and other social media platforms in China. But concerns about the potential misuse of deepfake technology coupled with a clause (now deleted) in Zao’s terms of use that gave it full ownership and copyright to content uploaded or created on it, in addition to “completely free, irrevocable, perpetual, transferrable, and re-licensable rights,” caused controversy.

In case you haven’t heard, #ZAO is a Chinese app which completely blew up since Friday. Best application of ‘Deepfake’-style AI facial replacement I’ve ever seen. Here’s an example of me as DiCaprio (generated in under 8 secs from that one photo in the thumbnail) 🤯 pic.twitter.com/1RpnJJ3wgT — Allan Xia (@AllanXia) September 1, 2019

By going viral quickly and being very easy to use (Zao’s videos can be generated from a single selfie, though it suggests that users upload photos from several angles for better results), the app has also focused more attention on deepfake technology and how it can potentially be used to spread misinformation or harass people.

Zao was released last Friday and quickly became the top free iOS app in China, according to App Annie. A statement posted on September 1 to Zao’s Weibo account says “we completely understand everybody’s concerns about the privacy issue. We are aware of the issue and we are thinking about how to fix the problems, we need a little time.” Its terms and conditions now say user-generated content will only be used by the company to improve the app and that all deleted content will be removed from its servers.

TechCrunch has contacted Zao for comment.