Update 1: 2017/07/17 5:53am PDT
In a statement given to Engadget, HTC has acknowledged that the ads were an error that they’re working on quickly removing:
Due to an error, some HTC customers have reported
There are a few places where advertising is acceptable. Your phone’s keyboard is definitely not one of them. The TouchPal keyboard, which HTC ships as the default system keyboard on many of its phones, has been updated to display ads.
[Update: HTC is working on a fix] HTC’s TouchPal Keyboard has started to show ads to users was written by the awesome team at Android Police.