The app has been criticized in multiple reports over recent years. For example, in 2016 Australian researchers CSIRO found that SuperVPN was flagged as malware by 13 engines at VirusTotal, the third highest score out of a field of 234. They were mostly classing it as adware-like rather than anything truly dangerous, and that still means most engines thought it was safe (and as we write its VirusTotal score is zero), but this indicates the app may be doing things differently to many other VPNs.
A 2016 Vulners report listed many other SuperVPN vulnerabilities and problems. We have no idea if the report was accurate, and the vulnerabilities may have been fixed in the meantime, anyway, but this is still a concern.
There's another potential issue in the app's permissions. It needs access to Device & App History (get running apps, read sensitive log data), Identity and Contacts, Location, Photos/Media/Files, Storage, Wi-Fi Connection Information and Device ID and Call Information. That covers the rights to see installed apps, browsing history, profile data and your file system.
