If I started a fruit distribution company and called it Rhombus, there probably wouldn't be an issue.
I can't say whether there is definitive trademark infringement here (Cube seems to offer analytics services and targets a niche market, differentiating its product). However, I can't help but feel that "Cube" is a reference to Square.
edit: Can someone please explain why this is being downvoted? I'd like to make sure my contributions are constructive.