In this report, we analyze the Windows, Android, and iOS versions of Tencent’s Sogou Input Method, the most popular Chinese-language input method in China. Our analysis found serious vulnerabilities in the app’s custom encryption system and how it encrypts sensitive data. These vulnerabilities could allow a network eavesdropper to decrypt sensitive communications sent by the app, including revealing all keystrokes being typed by the user. Following our disclosure of these vulnerabilities, Sogou released updated versions of the app that identified all of the issues we disclosed.
Vulnerabilities in Sogou Keyboard encryption expose keypresses to network eavesdropping.
Just to state the obvious for the less tech-literate out there: an open source one could do the same.
It’s just very easy for anyone to find out by inspecting the code, that’s why no developer in their right mind would pull such a move.