Safari extension pop out

I got my first Macbook couple of months ago and all of the sudden I started getting this annoying pop out on safari that installs an extension by itself, it only happens when I first start safari after turning on my macbook and it closes all my tabs when it pops out. I close Safari not interacting with the pop out and when I open Safari again it takes me to the apple web site with the name of the extension. I've tried deleting cache, cookies and history but it doesn't work. I even blocked extensions on safari and still happens, I also delete every single time the extension from the "Apps" section on Finder, and when I turn on my Mac there it is again. Please if anybody could help me it would be very appreciated. The extension is called SearchIt, and apparently is on the AppStore, I never tried to download it though.