### Comment:
Eyeballing their POS systems it does not appear to be the case. Unless I missed an announcement years ago or something. 
  
 edit: Looks like they do use Square for popups, see [here](https://pbs.twimg.com/media/DiLSNr_WsAAaK2v.jpg). But doesn't look like they use it in stores. 
  
 Square added Shake Shack CEO to board of directors on Jul 20, 2017.

### REPLY:
Square powers the payments for their self serve kiosks 
  
  https://fuzzproductions.com/work/shake-shack-kiosk

### END.