Chinese Characters Appearing at Bottom of Screen?

My mom came to me with a problem with her phone about how these chinese characters keep popping up on her phone about every 5 minutes or so. I got a look at it and tried to take a screenshot of the characters when they would appear on her phone, but it seemed like it knew when I would try to take a picture of it because when I would try to take a picture of it, it would only show for a split second, while without trying to take a picture of it, it would be on screen for a few seconds. The characters on the phone showed up as follows: 账号SDK进入测试环境 After I was finally able to get a shot of the characters by taking a video, I thought I found the source of what was happening in her file manager and deleted all the files that had SDK in them. 5 minutes later, she is still having the same problem, and I am wondering how I can make this go away. Has anybody else had this problem, or is it something specifically that my mom may have on her phone?