As it is a third-party application that is not available on Google Play Store or App Store, it can look suspicious to some users. Moreover, it might infect your device with a virus after downloading it. Applob is a useful application to download the premium apps that you want, but it may require you to download different other apps before you can download the one that you need.
So far no users have reported any issue with Applob, however, you still always be careful while using any untrusted app.