In this report, we examine cloud-based pinyin keyboard apps from nine vendors (Baidu, Honor, Huawei, iFlyTek, OPPO, Samsung, Tencent, Vivo, and Xiaomi) for vulnerabilities in how the apps transmit user keystrokes. Our analysis found that eight of the nine apps identified contained vulnerabilities that could be exploited to completely reveal the contents of users’ keystrokes in transit. We estimate that up to one billion users could be vulnerable to having all of their keystrokes intercepted, constituting a tremendous risk to user security.
TLDR:
This study mainly targets Pinyin input, the most popular Chinese input method (hence 1bn potentially affected).
Vulnerabilities were due to the keyboards’ use of the cloud for dictionaries used in IMEs (essentially a conversion engine). Such IMEs are must-haves for certain languages and converts A-Zs to other scripts. Lack of E2EE resulted in exposed keystrokes.
Personally I would recommend switching to something which uses a local dictionary. RIME is a good FOSS alternative and can be configured to work on Android via fcitx.
While the study doesn’t cover English keyboards, this is as good a reminder as any not to use in-built dictionaries in general unless you have to.