A Chinese app that allows users to convincingly exchange their faces with movies or TV characters quickly became one of the most downloaded apps in the country, triggering a privacy line.

The Zao app went viral as Chinese users seized the opportunity to see themselves act out scenes from well-known movies using deepfake technology. This has already prompted concerns elsewhere over potential misuse.

The company was forced to issue a statement on Sunday that promised a change that would be “free, irrevocable, permanent, transferable, and licensable” for the rights of all user-generated content.